class_docstr: Interface for defining a custom :class:`~ray.data.Dataset` datasource.
  
  To read a datasource into a dataset, use :meth:`~ray.data.read_datasource`.
class_docstr_tok: ["Interface","for","defining","a","custom",":","class",":","`","~ray.data.Dataset","`","datasource",".","To","read","a","datasource","into","a","dataset",",","use",":","meth",":","`","~ray.data.read_datasource","`","."]
docstr: Deprecated: Please implement create_reader() instead.
docstr_tok: ["Deprecated",":","Please","implement","create_reader","(",")","instead","."]
code: def prepare_read(
      self, parallelism: int, **read_args
  ) -> List["ReadTask"]:
      """Deprecated: Please implement create_reader() instead."""
      raise NotImplementedError
  
imports: import warnings
  from typing import Any, Callable, Iterable, List, Optional
  import numpy
  import ray
  from ray.data._internal.execution.interfaces import TaskContext
  from ray.data._internal.util import _check_pyarrow_version
  from ray.data.block import Block, BlockAccessor, BlockMetadata
  from ray.data.context import DataContext
  from ray.types import ObjectRef
  from ray.util.annotations import Deprecated, DeveloperAPI, PublicAPI
label_desc: Use image node_id 2 for calling the Datasource obj's underlying member method code with example usage: obj.prepare_read(parallelism) without return types