text: # Copyright (c) 2021, NVIDIA CORPORATION.  All rights reserved.
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #     http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  
  import copy
  import inspect
  import os
  import uuid
  from abc import abstractmethod
  from os import path
  from pathlib import Path
  from typing import Callable, Dict, List, Optional, Union
  
  import hydra
  import torch
  from omegaconf import DictConfig, OmegaConf, open_dict
  from pytorch_lightning import LightningModule, Trainer
  from pytorch_lightning.utilities import rank_zero_only
  
  from nemo.core import optim
  from nemo.core.classes.common import Model
  from nemo.core.connectors.save_restore_connector import SaveRestoreConnector
  from nemo.core.optim import prepare_lr_scheduler
  from nemo.utils import logging, model_utils
  from nemo.utils.app_state import AppState
  from nemo.utils.get_rank import is_global_rank_zero
  
  __all__ = ['ModelPT']
  
  
  class ModelPT(LightningModule, Model):
      """
      Interface for Pytorch-lightning based NeMo models
      """
  
      def __init__(self, cfg: DictConfig, trainer: Trainer = None):
          """
          Base class from which all NeMo models should inherit
  
          Args:
              cfg (DictConfig):  configuration object.
                  The cfg object should have (optionally) the following sub-configs:
  
                  * train_ds - to instantiate training dataset
                  * validation_ds - to instantiate validation dataset
                  * test_ds - to instantiate testing dataset
                  * optim - to instantiate optimizer with learning rate scheduler
  
              trainer (Optional): Pytorch Lightning Trainer instance
          """
          if trainer is not None and not isinstance(trainer, Trainer):
              raise ValueError(
                  f"trainer constructor argument must be either None or pytroch_lightning.Trainer. But got {type(trainer)} instead."
              )
          super().__init__()
  
          """
          Internal global flags that determine core functionality of ModelPT.
  
          _MODEL_IS_RESTORED:
              This flag determines the context of the model - whether the model is currently being
              restored or not.
              -   When set, it can be assumed that the model's will disable all automatic methods -
                  setup_training_data(), setup_validation/test_data() and their multi equivalents.
              -   If a model is being restored from a archive file (tarfile), it can be assumed that
                  under this context, the cwd is *inside* the tarfile itself.
  
          _MODEL_RESTORE_PATH:
              A string path to a a file from which the model is being restored.
              This file can either be a PyTorch Lightning Checkpoint, or a archive (tarfile) that contains
              artifact objects.
              If it is an archive file, during restoration, the cwd will be temporarily moved to inside the
              archive itself.
          """
          # set global vars in AppState
          app_state = AppState()
  
          # Convert config to a DictConfig
          cfg = model_utils.convert_model_config_to_dict_config(cfg)
  
          # Convert config to support Hydra 1.0+ instantiation
          cfg = model_utils.maybe_update_config_version(cfg)
  
          if 'target' not in cfg:
              # This is for Jarvis service.
              OmegaConf.set_struct(cfg, False)
              cfg.target = "{0}.{1}".format(self.__class__.__module__, self.__class__.__name__)
              OmegaConf.set_struct(cfg, True)
  
          self._cfg = cfg
  
          self.save_hyperparameters("cfg")
          self._train_dl = None
          self._validation_dl = None
          self._test_dl = None
          self._optimizer = None
          self._scheduler = None
          self.trainer = trainer  # reference required for self.*_rank
          self._trainer = self.trainer  # alias for backward compatibility
          self._save_restore_connector = SaveRestoreConnector()
  
          self._set_model_guid()
  
          # Set device_id in AppState
          if torch.cuda.is_available() and torch.cuda.current_device() is not None:
              app_state.device_id = torch.cuda.current_device()
  
          if self._cfg is not None and not self._is_model_being_restored():
              if 'train_ds' in self._cfg and self._cfg.train_ds is not None:
                  self.setup_training_data(self._cfg.train_ds)
  
              if 'validation_ds' in self._cfg and self._cfg.validation_ds is not None:
                  self.setup_multiple_validation_data(val_data_config=None)
  
              if 'test_ds' in self._cfg and self._cfg.test_ds is not None:
                  self.setup_multiple_test_data(test_data_config=None)
  
          else:
              if 'train_ds' in self._cfg and self._cfg.train_ds is not None:
                  logging.warning(
                      f"If you intend to do training or fine-tuning, please call the ModelPT.setup_training_data() method "
                      f"and provide a valid configuration file to setup the train data loader.\n"
                      f"Train config : \n{OmegaConf.to_yaml(self._cfg.train_ds)}"
                  )
  
              if 'validation_ds' in self._cfg and self._cfg.validation_ds is not None:
                  logging.warning(
                      f"If you intend to do validation, please call the ModelPT.setup_validation_data() or ModelPT.setup_multiple_validation_data() method "
                      f"and provide a valid configuration file to setup the validation data loader(s). \n"
                      f"Validation config : \n{OmegaConf.to_yaml(self._cfg.validation_ds)}"
                  )
              if 'test_ds' in self._cfg and self._cfg.test_ds is not None:
                  logging.warning(
                      f"Please call the ModelPT.setup_test_data() or ModelPT.setup_multiple_test_data() method "
                      f"and provide a valid configuration file to setup the test data loader(s).\n"
                      f"Test config : \n{OmegaConf.to_yaml(self._cfg.test_ds)}"
                  )
  
          # ModelPT wrappers over subclass implementations
          self.training_step = model_utils.wrap_training_step(self.training_step)
  
      def __init_subclass__(cls) -> None:
          cls._save_restore_connector = SaveRestoreConnector()
  
      def register_artifact(
          self, config_path: str, src: str, verify_src_exists: bool = True,
      ):
          """ Register model artifacts with this function. These artifacts (files) will be included inside .nemo file
              when model.save_to("mymodel.nemo") is called.
  
              How it works:
              1. It always returns existing absolute path which can be used during Model constructor call
                  EXCEPTION: src is None or "" in which case nothing will be done and src will be returned
              2. It will add (config_path, model_utils.ArtifactItem()) pair to self.artifacts
  
              If "src" is local existing path, then it will be returned in absolute path form.
              elif "src" starts with "nemo_file:unique_artifact_name":
                  .nemo will be untarred to a temporary folder location and an actual existing path will be returned
              else an error will be raised.
  
              WARNING: use .register_artifact calls in your models' constructors.
              The returned path is not guaranteed to exist after you have exited your model's constuctor.
  
              Args:
                  config_path (str): Artifact key. Usually corresponds to the model config.
                  src (str): Path to artifact.
                  verify_src_exists (bool): If set to False, then the artifact is optional and register_artifact will return None even if
                                            src is not found. Defaults to True.
                  save_restore_connector (SaveRestoreConnector): Can be overrided to add custom save and restore logic.
  
              Returns:
                  str: If src is not None or empty it always returns absolute path which is guaranteed to exists during model instnce life
          """
  
          app_state = AppState()
  
          if src is None or src == "":
              return src
  
          if not hasattr(self, 'artifacts'):
              self.artifacts = {}
  
          if self.artifacts is None:
              self.artifacts = {}
  
          if config_path in self.artifacts.keys():
              logging.warning(
                  f"You tried to register an artifact under config key={config_path} but an artifact for "
                  f"it has already been registered."
              )
  
          return self._save_restore_connector.register_artifact(self, config_path, src, verify_src_exists)
  
      def save_to(self, save_path: str):
          """
          Saves model instance (weights and configuration) into .nemo file
           You can use "restore_from" method to fully restore instance from .nemo file.
  
          .nemo file is an archive (tar.gz) with the following:
              model_config.yaml - model configuration in .yaml format. You can deserialize this into cfg argument for model's constructor
              model_wights.chpt - model checkpoint
  
          Args:
              save_path: Path to .nemo file where model instance should be saved
          """
  
          def maybe_make_save_dir(path: 'pathlib.Path'):
              if not path.parent.exists():
                  path.parent.mkdir(parents=True)
  
          save_path = Path(save_path).expanduser().resolve()
          app_state = AppState()
          if app_state.model_parallel_size is not None:
              if app_state.model_parallel_size > 1:
                  if type(self._save_restore_connector) == SaveRestoreConnector:
                      raise ValueError(
                          'Default NeMo SaveRestoreConnector will not work in model parallel mode. You should use a '
                          'connector which supports model parallel mode, such as NLPSaveRestoreConnector in NLP. You '
                          'can also use a custom one.'
                      )
              if app_state.data_parallel_rank == 0:
                  maybe_make_save_dir(save_path)
              # connector checks for ranks properly, no need to check here
              self._save_restore_connector.save_to(self, str(save_path))  # downstream tasks expect str, not Path
          elif is_global_rank_zero():
              maybe_make_save_dir(save_path)
              self._save_restore_connector.save_to(self, str(save_path))  # downstream tasks expect str, not Path
  
      @classmethod
      def restore_from(
          cls,
          restore_path: str,
          override_config_path: Optional[Union[OmegaConf, str]] = None,
          map_location: Optional[torch.device] = None,
          strict: bool = True,
          return_config: bool = False,
          save_restore_connector: SaveRestoreConnector = None,
          trainer: Optional[Trainer] = None,
      ):
          """
          Restores model instance (weights and configuration) from .nemo file.
  
          Args:
              restore_path: path to .nemo file from which model should be instantiated
              override_config_path: path to a yaml config that will override the internal
                  config file or an OmegaConf / DictConfig object representing the model config.
              map_location: Optional torch.device() to map the instantiated model to a device.
                  By default (None), it will select a GPU if available, falling back to CPU otherwise.
              strict: Passed to load_state_dict. By default True.
              return_config: If set to true, will return just the underlying config of the restored
                  model as an OmegaConf DictConfig object without instantiating the model.
              trainer: Optional, a pytorch lightning Trainer object that will be forwarded to the
                  instantiated model's constructor.
              save_restore_connector (SaveRestoreConnector): Can be overrided to add custom save and restore logic.
  
              Example:
                  ```
                  model = nemo.collections.asr.models.EncDecCTCModel.restore_from('asr.nemo')
                  assert isinstance(model, nemo.collections.asr.models.EncDecCTCModel)
                  ```
  
          Returns:
              An instance of type cls or its underlying config (if return_config is set).
          """
  
          if save_restore_connector is None:
              save_restore_connector = SaveRestoreConnector()
  
          restore_path = os.path.abspath(os.path.expanduser(restore_path))
          if not path.exists(restore_path):
              raise FileNotFoundError(f"Can't find {restore_path}")
  
          app_state = AppState()
          app_state.model_restore_path = restore_path
  
          cls.update_save_restore_connector(save_restore_connector)
          instance = cls._save_restore_connector.restore_from(
              cls, restore_path, override_config_path, map_location, strict, return_config, trainer
          )
          if isinstance(instance, ModelPT):
              instance._save_restore_connector = save_restore_connector
          return instance
  
      @classmethod
      def load_from_checkpoint(
          cls,
          checkpoint_path: str,
          *args,
          map_location: Optional[Union[Dict[str, str], str, torch.device, int, Callable]] = None,
          hparams_file: Optional[str] = None,
          strict: bool = True,
          **kwargs,
      ):
          """
          Loads ModelPT from checkpoint, with some maintenance of restoration.
          For documentation, please refer to LightningModule.load_from_checkpoin() documentation.
          """
          checkpoint = None
          try:
              cls._set_model_restore_state(is_being_restored=True)
  
              checkpoint = super().load_from_checkpoint(
                  checkpoint_path=checkpoint_path,
                  *args,
                  map_location=map_location,
                  hparams_file=hparams_file,
                  strict=strict,
                  **kwargs,
              )
  
          finally:
              cls._set_model_restore_state(is_being_restored=False)
          return checkpoint
  
      @abstractmethod
      def setup_training_data(self, train_data_config: Union[DictConfig, Dict]):
          """
          Setups data loader to be used in training
  
          Args:
              train_data_layer_config: training data layer parameters.
          Returns:
  
          """
          pass
  
      @abstractmethod
      def setup_validation_data(self, val_data_config: Union[DictConfig, Dict]):
          """
          Setups data loader to be used in validation
          Args:
  
              val_data_layer_config: validation data layer parameters.
          Returns:
  
          """
          pass
  
      def setup_test_data(self, test_data_config: Union[DictConfig, Dict]):
          """
          (Optionally) Setups data loader to be used in test
  
          Args:
              test_data_layer_config: test data layer parameters.
          Returns:
  
          """
          raise NotImplementedError()
  
      def setup_multiple_validation_data(self, val_data_config: Union[DictConfig, Dict]):
          """
          (Optionally) Setups data loader to be used in validation, with support for multiple data loaders.
  
          Args:
              val_data_layer_config: validation data layer parameters.
          """
          # Set some placeholder overriden by helper method
          self._val_dl_idx = 0
          self._validation_names = None
          self._validation_dl = None  # type: torch.utils.data.DataLoader
  
          # preserve config
          self._update_dataset_config(dataset_name='validation', config=val_data_config)
  
          try:
              self._multi_dataset_mode = True
              model_utils.resolve_validation_dataloaders(model=self)
          finally:
              self._multi_dataset_mode = False
  
          if self._validation_names is None:
              if self._validation_dl is not None and type(self._validation_dl) in [list, tuple]:
                  self._validation_names = ['val_{}_'.format(idx) for idx in range(len(self._validation_dl))]
  
      def setup_multiple_test_data(self, test_data_config: Union[DictConfig, Dict]):
          """
          (Optionally) Setups data loader to be used in test, with support for multiple data loaders.
  
          Args:
              test_data_layer_config: test data layer parameters.
          """
          # Set some placeholder overriden by helper method
          self._test_dl_idx = 0
          self._test_names = None
          self._test_dl = None  # type: torch.utils.data.DataLoader
  
          # preserve config
          self._update_dataset_config(dataset_name='test', config=test_data_config)
  
          try:
              self._multi_dataset_mode = True
              model_utils.resolve_test_dataloaders(model=self)
          finally:
              self._multi_dataset_mode = False
  
          if self._test_names is None:
              if self._test_dl is not None and type(self._test_dl) in [list, tuple]:
                  self._test_names = ['test_{}_'.format(idx) for idx in range(len(self._test_dl))]
  
      def setup_optimization(self, optim_config: Optional[Union[DictConfig, Dict]] = None):
          """
          Prepares an optimizer from a string name and its optional config parameters.
  
          Args:
              optim_config: A dictionary containing the following keys:
  
                  * "lr": mandatory key for learning rate. Will raise ValueError if not provided.
                  * "optimizer": string name pointing to one of the available optimizers in the registry. \
                  If not provided, defaults to "adam".
                  * "opt_args": Optional list of strings, in the format "arg_name=arg_value". \
                  The list of "arg_value" will be parsed and a dictionary of optimizer kwargs \
                  will be built and supplied to instantiate the optimizer.
          """
          # If config was not explicitly passed to us
          if optim_config is None:
              # See if internal config has `optim` namespace
              if self._cfg is not None and hasattr(self._cfg, 'optim'):
                  optim_config = self._cfg.optim
  
          # If config is still None, or internal config has no Optim, return without instantiation
          if optim_config is None:
              logging.info('No optimizer config provided, therefore no optimizer was created')
              return
  
          else:
              # Preserve the configuration
              if not isinstance(optim_config, DictConfig):
                  optim_config = OmegaConf.create(optim_config)
  
              # See if internal config has `optim` namespace before preservation
              if self._cfg is not None and hasattr(self._cfg, 'optim'):
                  if self._cfg.optim is None:
                      self._cfg.optim = copy.deepcopy(optim_config)
                  else:
                      with open_dict(self._cfg.optim):
                          self._cfg.optim = copy.deepcopy(optim_config)
  
          # Setup optimizer and scheduler
          if optim_config is not None and isinstance(optim_config, DictConfig):
              optim_config = OmegaConf.to_container(optim_config, resolve=True)
  
          if self._trainer is None:
              logging.warning(f"Trainer wasn't specified in model constructor. Make sure that you really wanted it.")
  
          if 'sched' in optim_config and self._trainer is not None:
              if not isinstance(self._trainer.accumulate_grad_batches, int):
                  raise ValueError("We do not currently support gradient acculumation that is not an integer.")
              if self._trainer.max_steps is None or self.trainer.max_steps < 0:
                  # Store information needed to calculate max_steps
                  optim_config['sched']['t_max_epochs'] = self._trainer.max_epochs
                  optim_config['sched']['t_accumulate_grad_batches'] = self._trainer.accumulate_grad_batches
                  optim_config['sched']['t_limit_train_batches'] = self._trainer.limit_train_batches
                  if self._trainer.accelerator is None:
                      optim_config['sched']['t_num_workers'] = self._trainer.num_gpus or 1
                  elif self._trainer.accelerator == "ddp_cpu":
                      optim_config['sched']['t_num_workers'] = self._trainer.num_processes * self._trainer.num_nodes
                  elif self._trainer.accelerator == "ddp":
                      optim_config['sched']['t_num_workers'] = self._trainer.num_gpus * self._trainer.num_nodes
                  else:
                      logging.warning(
                          f"The lightning trainer received accelerator: {self._trainer.accelerator}. We "
                          "recommend to use 'ddp' instead."
                      )
                      optim_config['sched']['t_num_workers'] = self._trainer.num_gpus * self._trainer.num_nodes
              else:
                  optim_config['sched']['max_steps'] = self._trainer.max_steps
  
          # Force into DictConfig from nested structure
          optim_config = OmegaConf.create(optim_config)
          # Get back nested dict so we its mutable
          optim_config = OmegaConf.to_container(optim_config, resolve=True)
  
          # Extract scheduler config if inside optimizer config
          if 'sched' in optim_config:
              scheduler_config = optim_config.pop('sched')
          else:
              scheduler_config = None
  
          # Check if caller provided optimizer name, default to Adam otherwise
          optimizer_cls = optim_config.get('_target_', None)
  
          if optimizer_cls is None:
              # Try to get optimizer name for dynamic resolution, defaulting to Adam
              optimizer_name = optim_config.get('name', 'adam')
          else:
              if inspect.isclass(optimizer_cls):
                  optimizer_name = optimizer_cls.__name__.lower()
              else:
                  # resolve the class name (lowercase) from the class path if not provided
                  optimizer_name = optimizer_cls.split(".")[-1].lower()
  
          # We are guarenteed to have lr since it is required by the argparser
          # But maybe user forgot to pass it to this function
          lr = optim_config.get('lr', None)
  
          # Check if caller has optimizer kwargs, default to empty dictionary
          if 'args' in optim_config:
              optimizer_args = optim_config.pop('args')
              optimizer_args = optim.parse_optimizer_args(optimizer_name, optimizer_args)
          else:
              optimizer_args = copy.deepcopy(optim_config)
  
              # Remove extra parameters from optimizer_args nest
              # Assume all other parameters are to be passed into optimizer constructor
              optimizer_args.pop('name', None)
              optimizer_args.pop('cls', None)
              optimizer_args.pop('lr', None)
  
          # Adaptive schedulers don't need `lr`
          if lr is not None:
              optimizer_args['lr'] = lr
  
          # Actually instantiate the optimizer
          if optimizer_cls is not None:
              if inspect.isclass(optimizer_cls):
                  optimizer = optimizer_cls(self.parameters(), **optimizer_args)
                  logging.info("Optimizer config = %s", str(optimizer))
  
                  self._optimizer = optimizer
  
              else:
                  # Attempt class path resolution
                  try:
                      optimizer_cls = OmegaConf.create({'_target_': optimizer_cls})
                      if lr is not None:
                          optimizer_config = {'lr': lr}
                      else:
                          optimizer_config = {}
                      optimizer_config.update(optimizer_args)
  
                      optimizer_instance = hydra.utils.instantiate(
                          optimizer_cls, self.parameters(), **optimizer_config
                      )  # type: DictConfig
  
                      logging.info("Optimizer config = %s", str(optimizer_instance))
  
                      self._optimizer = optimizer_instance
  
                  except Exception as e:
                      logging.error(
                          "Could not instantiate class path - {} with kwargs {}".format(
                              optimizer_cls, str(optimizer_config)
                          )
                      )
                      raise e
  
          else:
              optimizer = optim.get_optimizer(optimizer_name)
              optimizer = optimizer(self.parameters(), **optimizer_args)
  
              logging.info("Optimizer config = %s", str(optimizer))
  
              self._optimizer = optimizer
  
          # Try to instantiate scheduler for optimizer
          self._scheduler = prepare_lr_scheduler(
              optimizer=self._optimizer, scheduler_config=scheduler_config, train_dataloader=self._train_dl
          )
  
          # Return the optimizer with/without scheduler
          # This return allows multiple optimizers or schedulers to be created
          return self._optimizer, self._scheduler
  
      def configure_optimizers(self):
          self.setup_optimization()
  
          if self._scheduler is None:
              return self._optimizer
          else:
              return [self._optimizer], [self._scheduler]
  
      def train_dataloader(self):
          if self._train_dl is not None:
              return self._train_dl
  
      def val_dataloader(self):
          if self._validation_dl is not None:
              return self._validation_dl
  
      def test_dataloader(self):
          if self._test_dl is not None:
              return self._test_dl
  
      def validation_epoch_end(
          self, outputs: Union[List[Dict[str, torch.Tensor]], List[List[Dict[str, torch.Tensor]]]]
      ) -> Optional[Dict[str, Dict[str, torch.Tensor]]]:
          """
          Default DataLoader for Validation set which automatically supports multiple data loaders
          via `multi_validation_epoch_end`.
  
          If multi dataset support is not required, override this method entirely in base class.
          In such a case, there is no need to implement `multi_validation_epoch_end` either.
  
          .. note::
              If more than one data loader exists, and they all provide `val_loss`,
              only the `val_loss` of the first data loader will be used by default.
              This default can be changed by passing the special key `val_dl_idx: int`
              inside the `validation_ds` config.
  
          Args:
              outputs: Single or nested list of tensor outputs from one or more data loaders.
  
          Returns:
              A dictionary containing the union of all items from individual data_loaders,
              along with merged logs from all data loaders.
          """
          # Case where we dont provide data loaders
          if outputs is not None and len(outputs) == 0:
              return {}
  
          # Case where we provide exactly 1 data loader
          if type(outputs[0]) == dict:
              output_dict = self.multi_validation_epoch_end(outputs, dataloader_idx=0)
  
              if output_dict is not None and 'log' in output_dict:
                  self.log_dict(output_dict.pop('log'), on_epoch=True)
  
              return output_dict
  
          else:  # Case where we provide more than 1 data loader
              output_dict = {'log': {}}
  
              # The output is a list of list of dicts, outer list corresponds to dataloader idx
              for dataloader_idx, val_outputs in enumerate(outputs):
                  # Get prefix and dispatch call to multi epoch end
                  dataloader_prefix = self.get_validation_dataloader_prefix(dataloader_idx)
                  dataloader_logs = self.multi_validation_epoch_end(val_outputs, dataloader_idx=dataloader_idx)
  
                  # If result was not provided, generate empty dict
                  dataloader_logs = dataloader_logs or {}
  
                  # Perform `val_loss` resolution first (if provided outside logs)
                  if 'val_loss' in dataloader_logs:
                      if 'val_loss' not in output_dict and dataloader_idx == self._val_dl_idx:
                          output_dict['val_loss'] = dataloader_logs['val_loss']
  
                  # For every item in the result dictionary
                  for k, v in dataloader_logs.items():
                      # If the key is `log`
                      if k == 'log':
                          # Parse every element of the log, and attach the prefix name of the data loader
                          log_dict = {}
  
                          for k_log, v_log in v.items():
                              # If we are logging the metric, but dont provide it at result level,
                              # store it twice - once in log and once in result level.
                              # Also mark log with prefix name to avoid log level clash with other data loaders
                              if k_log not in output_dict['log'] and dataloader_idx == self._val_dl_idx:
                                  new_k_log = k_log
  
                                  # Also insert duplicate key with prefix for ease of comparison / avoid name clash
                                  log_dict[dataloader_prefix + k_log] = v_log
  
                              else:
                                  # Simply prepend prefix to key and save
                                  new_k_log = dataloader_prefix + k_log
  
                              # Store log value
                              log_dict[new_k_log] = v_log
  
                          # Update log storage of individual data loader
                          output_logs = output_dict['log']
                          output_logs.update(log_dict)
  
                          # Update global log storage
                          output_dict['log'] = output_logs
  
                      else:
                          # If any values are stored outside 'log', simply prefix name and store
                          new_k = dataloader_prefix + k
                          output_dict[new_k] = v
  
              if 'log' in output_dict:
                  self.log_dict(output_dict.pop('log'), on_epoch=True)
  
              # return everything else
              return output_dict
  
      def test_epoch_end(
          self, outputs: Union[List[Dict[str, torch.Tensor]], List[List[Dict[str, torch.Tensor]]]]
      ) -> Optional[Dict[str, Dict[str, torch.Tensor]]]:
          """
          Default DataLoader for Test set which automatically supports multiple data loaders
          via `multi_test_epoch_end`.
  
          If multi dataset support is not required, override this method entirely in base class.
          In such a case, there is no need to implement `multi_test_epoch_end` either.
  
          .. note::
              If more than one data loader exists, and they all provide `test_loss`,
              only the `test_loss` of the first data loader will be used by default.
              This default can be changed by passing the special key `test_dl_idx: int`
              inside the `test_ds` config.
  
          Args:
              outputs: Single or nested list of tensor outputs from one or more data loaders.
  
          Returns:
              A dictionary containing the union of all items from individual data_loaders,
              along with merged logs from all data loaders.
          """
          # Case where we dont provide data loaders
          if outputs is not None and len(outputs) == 0:
              return {}
  
          # Case where we provide exactly 1 data loader
          if type(outputs[0]) == dict:
              output_dict = self.multi_test_epoch_end(outputs, dataloader_idx=0)
  
              if output_dict is not None and 'log' in output_dict:
                  self.log_dict(output_dict.pop('log'), on_epoch=True)
  
              return output_dict
  
          else:  # Case where we provide more than 1 data loader
              output_dict = {'log': {}}
  
              # The output is a list of list of dicts, outer list corresponds to dataloader idx
              for dataloader_idx, test_outputs in enumerate(outputs):
                  # Get prefix and dispatch call to multi epoch end
                  dataloader_prefix = self.get_test_dataloader_prefix(dataloader_idx)
                  dataloader_logs = self.multi_test_epoch_end(test_outputs, dataloader_idx=dataloader_idx)
  
                  # If result was not provided, generate empty dict
                  dataloader_logs = dataloader_logs or {}
  
                  # Perform `test_loss` resolution first (if provided outside logs)
                  if 'test_loss' in dataloader_logs:
                      if 'test_loss' not in output_dict and dataloader_idx == self._test_dl_idx:
                          output_dict['test_loss'] = dataloader_logs['test_loss']
  
                  # For every item in the result dictionary
                  for k, v in dataloader_logs.items():
                      # If the key is `log`
                      if k == 'log':
                          # Parse every element of the log, and attach the prefix name of the data loader
                          log_dict = {}
                          for k_log, v_log in v.items():
                              # If we are logging the loss, but dont provide it at result level,
                              # store it twice - once in log and once in result level.
                              # Also mark log with prefix name to avoid log level clash with other data loaders
                              if k_log not in output_dict['log'] and dataloader_idx == self._test_dl_idx:
                                  new_k_log = k_log
  
                                  # Also insert duplicate key with prefix for ease of comparison / avoid name clash
                                  log_dict[dataloader_prefix + k_log] = v_log
  
                              else:
                                  # Simply prepend prefix to key and save
                                  new_k_log = dataloader_prefix + k_log
  
                              log_dict[new_k_log] = v_log
  
                          # Update log storage of individual data loader
                          output_logs = output_dict.get('log', {})
                          output_logs.update(log_dict)
  
                          # Update global log storage
                          output_dict['log'] = output_logs
  
                      else:
                          # If any values are stored outside 'log', simply prefix name and store
                          new_k = dataloader_prefix + k
                          output_dict[new_k] = v
  
              if 'log' in output_dict:
                  self.log_dict(output_dict.pop('log'), on_epoch=True)
  
              # return everything else
              return output_dict
  
      def multi_validation_epoch_end(
          self, outputs: List[Dict[str, torch.Tensor]], dataloader_idx: int = 0
      ) -> Optional[Dict[str, Dict[str, torch.Tensor]]]:
          """
          Adds support for multiple validation datasets. Should be overriden by subclass,
          so as to obtain appropriate logs for each of the dataloaders.
  
          Args:
              outputs: Same as that provided by LightningModule.validation_epoch_end()
                  for a single dataloader.
              dataloader_idx: int representing the index of the dataloader.
  
          Returns:
              A dictionary of values, optionally containing a sub-dict `log`,
              such that the values in the log will be pre-pended by the dataloader prefix.
          """
          logging.warning(
              "Multi data loader support has been enabled, but "
              "`multi_validation_epoch_end(outputs, dataloader_idx) has not been implemented.\n"
              "If you require multi data loader support for validation sets, please override this method.\n"
              "If you do not require multi data loader support, please instead override "
              "`validation_epoch_end(outputs)."
          )
  
      def multi_test_epoch_end(
          self, outputs: List[Dict[str, torch.Tensor]], dataloader_idx: int = 0
      ) -> Optional[Dict[str, Dict[str, torch.Tensor]]]:
          """
          Adds support for multiple test datasets. Should be overriden by subclass,
          so as to obtain appropriate logs for each of the dataloaders.
  
          Args:
              outputs: Same as that provided by LightningModule.validation_epoch_end()
                  for a single dataloader.
              dataloader_idx: int representing the index of the dataloader.
  
          Returns:
              A dictionary of values, optionally containing a sub-dict `log`,
              such that the values in the log will be pre-pended by the dataloader prefix.
          """
          logging.warning(
              "Multi data loader support has been enabled, but "
              "`multi_test_epoch_end(outputs, dataloader_idx) has not been implemented.\n"
              "If you require multi data loader support for validation sets, please override this method.\n"
              "If you do not require multi data loader support, please instead override "
              "`test_epoch_end(outputs)."
          )
  
      def get_validation_dataloader_prefix(self, dataloader_idx: int = 0) -> str:
          """
          Get the name of one or more data loaders, which will be prepended to all logs.
  
          Args:
              dataloader_idx: Index of the data loader.
  
          Returns:
              str name of the data loader at index provided.
          """
          return self._validation_names[dataloader_idx]
  
      def get_test_dataloader_prefix(self, dataloader_idx: int = 0) -> str:
          """
          Get the name of one or more data loaders, which will be prepended to all logs.
  
          Args:
              dataloader_idx: Index of the data loader.
  
          Returns:
              str name of the data loader at index provided.
          """
          return self._test_names[dataloader_idx]
  
      @rank_zero_only
      def maybe_init_from_pretrained_checkpoint(self, cfg: OmegaConf, map_location: str = 'cpu'):
          """
          Initializes a given model with the parameters obtained via specific config arguments.
          The state dict of the provided model will be updated with `strict=False` setting so as to prevent
          requirement of exact model parameters matching.
  
          Initializations:
              init_from_nemo_model: Str path to a .nemo model, which will be instantiated in order
                  to extract the state dict.
  
              init_from_pretrained_model: Str name of a pretrained model checkpoint (obtained via cloud).
                  The model will be downloaded (or a cached copy will be used), instantiated and then
                  its state dict will be extracted.
  
              init_from_ptl_ckpt: Str name of a Pytorch Lightning checkpoint file. It will be loaded and
                  the state dict will extracted.
  
          Args:
              cfg: The config used to instantiate the model. It need only contain one of the above keys.
              map_location: str or torch.device() which represents where the intermediate state dict
                  (from the pretrained model or checkpoint) will be loaded.
  
          """
          args = ['init_from_nemo_model', 'init_from_pretrained_model', 'init_from_ptl_ckpt']
          arg_matches = [(1 if arg in cfg and arg is not None else 0) for arg in args]
  
          if sum(arg_matches) == 0:
              # model weights do not need to be restored
              return
  
          if sum(arg_matches) > 1:
              raise ValueError(
                  f"Cannot pass more than one model initialization arguments to config!\n"
                  f"Found : {[args[idx] for idx, arg_present in enumerate(arg_matches) if arg_present]}"
              )
  
          if 'init_from_nemo_model' in cfg and cfg.init_from_nemo_model is not None:
              with open_dict(cfg):
                  # Restore model
                  model_path = cfg.pop('init_from_nemo_model')
                  restored_model = self.restore_from(
                      model_path, map_location=map_location, strict=cfg.get("init_strict", True)
                  )
  
                  # Restore checkpoint into current model
                  self.load_state_dict(restored_model.state_dict(), strict=False)
                  logging.info(f'Model checkpoint restored from nemo file with path : `{model_path}`')
  
                  del restored_model
  
          if 'init_from_pretrained_model' in cfg and cfg.init_from_pretrained_model is not None:
              with open_dict(cfg):
                  # Restore model
                  model_name = cfg.pop('init_from_pretrained_model')
  
                  # Check if model is being resumed or not - only works if `Trainer` is attached to model
                  if hasattr(self, 'trainer') and self.trainer is not None:
                      trainer = self.trainer
                      if (
                          hasattr(trainer, 'resume_from_checkpoint')
                          and trainer.checkpoint_connector.resume_checkpoint_path is not None
                      ):
                          logging.info(
                              "Model training is being resumed via Pytorch Lightning.\n"
                              "Initialization from pretrained model (via cloud) will be skipped."
                          )
                          return
  
                  restored_model = self.from_pretrained(
                      model_name, map_location=map_location, strict=cfg.get("init_strict", True)
                  )
  
                  # Restore checkpoint into current model
                  self.load_state_dict(restored_model.state_dict(), strict=False)
                  logging.info(f'Model checkpoint restored from pretrained chackpoint with name : `{model_name}`')
  
                  del restored_model
  
          if 'init_from_ptl_ckpt' in cfg and cfg.init_from_ptl_ckpt is not None:
              with open_dict(cfg):
                  # Restore checkpoint
                  ckpt_path = cfg.pop('init_from_ptl_ckpt')
                  ckpt = torch.load(ckpt_path, map_location=map_location)
  
                  # Restore checkpoint into current model
                  self.load_state_dict(ckpt['state_dict'], strict=False)
                  logging.info(f'Model checkpoint restored from pytorch lightning chackpoint with path : `{ckpt_path}`')
  
                  del ckpt
  
      def teardown(self, stage: str):
          """
          Called at the end of fit and test.
  
          Args:
              stage: either 'fit' or 'test'
          """
          if stage == 'fit':
              # Update env variable to bypass multi gpu issue after training
              # This fix affects usage of trainer.test() after trainer.train()
              # If trainer.train() was done on multiple GPUs, then trainer.test()
              # will try to do ddp, even if its a new Trainer object with just 1 GPU.
              # Temporary patch to fix that
              if 'PL_TRAINER_GPUS' in os.environ:
                  os.environ.pop('PL_TRAINER_GPUS')
  
          super().teardown(stage)
  
      @classmethod
      def extract_state_dict_from(
          cls,
          restore_path: str,
          save_dir: str,
          split_by_module: bool = False,
          save_restore_connector: SaveRestoreConnector = None,
      ):
          """
          Extract the state dict(s) from a provided .nemo tarfile and save it to a directory.
  
          Args:
              restore_path: path to .nemo file from which state dict(s) should be extracted
              save_dir: directory in which the saved state dict(s) should be stored
              split_by_module: bool flag, which determins whether the output checkpoint should
                  be for the entire Model, or the individual module's that comprise the Model
              save_restore_connector (SaveRestoreConnector): Can be overrided to add custom save and restore logic.
  
          Example:
              To convert the .nemo tarfile into a single Model level PyTorch checkpoint
              ::
              state_dict = nemo.collections.asr.models.EncDecCTCModel.extract_state_dict_from('asr.nemo', './asr_ckpts')
  
  
              To restore a model from a Model level checkpoint
              ::
              model = nemo.collections.asr.models.EncDecCTCModel(cfg)  # or any other method of restoration
              model.load_state_dict(torch.load("./asr_ckpts/model_weights.ckpt"))
  
  
              To convert the .nemo tarfile into multiple Module level PyTorch checkpoints
              ::
              state_dict = nemo.collections.asr.models.EncDecCTCModel.extract_state_dict_from('asr.nemo', './asr_ckpts', split_by_module=True)
  
  
              To restore a module from a Module level checkpoint
              ::
              model = nemo.collections.asr.models.EncDecCTCModel(cfg)  # or any other method of restoration
  
              # load the individual components
              model.preprocessor.load_state_dict(torch.load("./asr_ckpts/preprocessor.ckpt"))
              model.encoder.load_state_dict(torch.load("./asr_ckpts/encoder.ckpt"))
              model.decoder.load_state_dict(torch.load("./asr_ckpts/decoder.ckpt"))
  
  
          Returns:
              The state dict that was loaded from the original .nemo checkpoint
          """
          if save_restore_connector is None:
              save_restore_connector = SaveRestoreConnector()
  
          if not path.exists(restore_path):
              raise FileExistsError(f"Can't find {restore_path}")
  
          cls.update_save_restore_connector(save_restore_connector)
          state_dict = cls._save_restore_connector.extract_state_dict_from(restore_path, save_dir, split_by_module)
          return state_dict
  
      def prepare_test(self, trainer: 'Trainer') -> bool:
          """
          Helper method to check whether the model can safely be tested
          on a dataset after training (or loading a checkpoint).
  
          ::
  
              trainer = Trainer()
              if model.prepare_test(trainer):
                  trainer.test(model)
  
          Returns:
              bool which declares the model safe to test. Provides warnings if it has to
              return False to guide the user.
          """
          if not hasattr(self._cfg, 'test_ds'):
              logging.info("No `test_ds` config found within the manifest.")
              return False
  
          # Replace ddp multi-gpu until PTL has a fix
          DDP_WARN = """\n\nDuring testing, it is currently advisable to construct a new Trainer "
                      "with single GPU and no DDP to obtain accurate results.
                      "Following pattern should be used: "
                      "gpu = 1 if cfg.trainer.gpus != 0 else 0"
                      "trainer = Trainer(gpus=gpu)"
                      "if model.prepare_test(trainer):"
                      "  trainer.test(model)\n\n"""
  
          if trainer is not None:
              if trainer.num_gpus > 1:
                  logging.warning(DDP_WARN)
                  return False
  
          # Assign trainer to the model
          self.set_trainer(trainer)
          return True
  
      def set_trainer(self, trainer: Trainer):
          """
          Set an instance of Trainer object.
  
          Args:
              trainer: PyTorch Lightning Trainer object.
          """
          self.trainer = trainer
          self._trainer = trainer
          self.set_world_size(self._trainer)
  
      def set_world_size(self, trainer: Trainer):
          """
          Determines the world size from the PyTorch Lightning Trainer.
          And then updates AppState.
  
          Args:
              trainer (Trainer): PyTorch Lightning Trainer object
          """
          # Update AppState with world information from trainer
          if isinstance(trainer, Trainer):
              app_state = AppState()
              if self._trainer.num_gpus and self._trainer.num_nodes:
                  app_state.world_size = self._trainer.num_gpus * self._trainer.num_nodes
          else:
              logging.warning(f'World size can only be set by PyTorch Lightning Trainer.')
  
      def _update_dataset_config(self, dataset_name: str, config: Optional[Union[DictConfig, Dict]]):
          """
          Update the config (if not None) of the dataset by given name.
          Preserves said config after updating.
  
          Args:
              dataset_name: str name of the dataset whose config is being updated.
                  Can be one of `train`, `validation` and `test`.
              config: Optional DictConfig or dict. If None is passed, this method simply returns.
                  If dict is passed, it is cast into a DictConfig.
                  The internal config is updated with the passed config.
          """
          if hasattr(self, '_multi_dataset_mode') and self._multi_dataset_mode is True:
              return
  
          if config is not None:
              if not isinstance(config, DictConfig):
                  config = OmegaConf.create(config)
  
              if dataset_name in ['train', 'validation', 'test']:
                  OmegaConf.set_struct(self.cfg, False)
  
                  key_name = dataset_name + "_ds"
                  self.cfg[key_name] = config
  
                  OmegaConf.set_struct(self.cfg, True)
  
                  # Update hyper parameters by calling property setter
                  self.cfg = self._cfg
              else:
                  raise ValueError("`dataset_name` when updating config must be one of [train, validation, test]")
  
      @property
      def num_weights(self):
          """
          Utility property that returns the total number of parameters of the Model.
          """
          num: int = 0
          for p in self.parameters():
              if p.requires_grad:
                  num += p.numel()
          return num
  
      @property
      def cfg(self):
          """
          Property that holds the finalized internal config of the model.
  
          Note:
              Changes to this config are not reflected in the state of the model.
              Please create a new model using an updated config to properly update the model.
          """
          return self._cfg
  
      @cfg.setter
      def cfg(self, cfg):
          """
          Property that holds the finalized internal config of the model.
  
          Note:
              Changes to this config are not reflected in the state of the model.
              Please create a new model using an updated config to properly update the model.
          """
          self._cfg = cfg
          self._set_hparams(OmegaConf.create({'cfg': self._cfg}))
  
      @staticmethod
      def _is_model_being_restored() -> bool:
          app_state = AppState()
          return app_state.is_model_being_restored
  
      @staticmethod
      def _set_model_restore_state(is_being_restored: bool, folder: str = None):
          app_state = AppState()
          app_state.is_model_being_restored = is_being_restored
          app_state.nemo_file_folder = folder
  
      def _set_model_guid(self):
          if not hasattr(self, 'model_guid'):
              appstate = AppState()
  
              # Generate a unique uuid for the instance
              # also determine if the model is being restored or not, and preserve the path
              self.model_guid = str(uuid.uuid4())
              if self._is_model_being_restored():
                  restore_path = appstate.model_restore_path
              else:
                  restore_path = None
  
              appstate.register_model_guid(self.model_guid, restoration_path=restore_path)
  
      @classmethod
      def update_save_restore_connector(cls, save_restore_connector):
          if hasattr(cls, '_save_restore_connector'):
              cls._save_restore_connector = save_restore_connector
          else:
              setattr(cls, '_save_restore_connector', save_restore_connector)
  