code: def split_input(cls, mapper_spec):
      
      batch_size = int(_get_params(mapper_spec).get(
          cls.BATCH_SIZE_PARAM, cls._BATCH_SIZE))
      shard_count = mapper_spec.shard_count
      namespace_ranges = namespace_range.NamespaceRange.split(shard_count,
                                                              contiguous=True)
      return [NamespaceInputReader(ns_range, batch_size)
              for ns_range in namespace_ranges]
docs: Returns a list of input readers for the input spec.
  
      Args:
        mapper_spec: The MapperSpec for this InputReader.
  
      Returns:
        A list of InputReaders.