code: def get_handler(backend, rank, size):
      if backend == "horovod":
          return HorovodDatasetHanlder(rank, size)
  
      if backend == "tf-distributed":
          return TFDistributedDatasetHandler(rank, size)
  
      if backend == "tf-local":
          return LocalDatasetHandler(rank, size)
  
      raise Exception(f"invalid backend: {backend}")
  
imports: import logging
  import json
  import os
  import numpy
  import ray
  from contextlib import closing
  import logging
  import socket
  from zoo.orca.data.utils import ray_partitions_get_data_label
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: HorovodDatasetHanlder, TFDistributedDatasetHandler, LocalDatasetHandler