code: def get_handler(backend, rank, size):
      if backend == "tf-distributed":
          return TFDistributedDatasetHandler(rank, size)
  
      if backend == "tf-local":
          return LocalDatasetHandler(rank, size)
  
      invalidInputError(False, f"invalid backend: {backend}")
  
imports: import json
  import os
  import tempfile
  import shutil
  import copy
  import tensorflow
  from bigdl.orca.data.utils import partition_get_data_label
  from bigdl.orca.data.file import exists
  from bigdl.orca.learn.utils import save_pkl, duplicate_stdout_stderr_to_file, get_rank, process_tensorboard_in_callbacks, save_model, load_model, replace_specific_object_from_callbacks
  from bigdl.orca.learn.log_monitor import LogMonitor
  from bigdl.orca.learn.tf2.callbacks import ModelCheckpoint
  from bigdl.dllib.utils.log4Error import *
label_desc: Use image node_id 7 for calling the DatasetHandler obj's underlying member method code with example usage: obj.get_handler(backend, rank, size) and returns: TFDistributedDatasetHandler, LocalDatasetHandler