class_docstr: HiFi-GAN model (https://arxiv.org/abs/2010.05646) that is used to generate audio from mel spectrogram.
class_docstr_tok: ["HiFi-GAN","model","(","https",":","\/\/arxiv.org\/abs\/2010.05646",")","that","is","used","to","generate","audio","from","mel","spectrogram","."]
code: def _process_batch(self, batch):
      if self.input_as_mel:
          audio, audio_len, audio_mel = batch
          audio_mel_len = [audio_mel.shape[1]] * audio_mel.shape[0]
          return audio, audio_len, audio_mel, audio_mel_len
  
      if (
          self.ds_class
          == "nemo.collections.tts.data.vocoder_dataset.VocoderDataset"
      ):
          audio = batch.get("audio")
          audio_len = batch.get("audio_lens")
      else:
          audio, audio_len = batch
  
      audio_mel, audio_mel_len = self.audio_to_melspec_precessor(
          audio, audio_len
      )
      return audio, audio_len, audio_mel, audio_mel_len
  
imports: import itertools
  from pathlib import Path
  import torch
  import torch.nn.functional
  from hydra.utils import instantiate
  from omegaconf import DictConfig, OmegaConf, open_dict
  from pytorch_lightning.loggers.wandb import WandbLogger
  from nemo.collections.tts.losses.hifigan_losses import DiscriminatorLoss, FeatureMatchingLoss, GeneratorLoss
  from nemo.collections.tts.models.base import Vocoder
  from nemo.collections.tts.modules.hifigan_modules import MultiPeriodDiscriminator, MultiScaleDiscriminator
  from nemo.collections.tts.parts.utils.callbacks import LoggingCallback
  from nemo.collections.tts.parts.utils.helpers import get_batch_size, get_num_workers, plot_spectrogram_to_numpy
  from nemo.core.classes import Exportable
  from nemo.core.classes.common import PretrainedModelInfo, typecheck
  from nemo.core.neural_types.elements import AudioSignal, MelSpectrogramType
  from nemo.core.neural_types.neural_type import NeuralType
  from nemo.core.optim.lr_scheduler import compute_max_steps, prepare_lr_scheduler
  from nemo.utils import logging, model_utils
label_desc: Use image node_id 11 for calling the HifiGanModel obj's underlying member method code with example usage: obj._process_batch(batch) and returns: audio,  audio_len,  audio_mel,  audio_mel_len, audio,  audio_len,  audio_mel,  audio_mel_len