code: def estimate_inmemory_data_size(self) -> Optional[int]:
      return None
  
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 _LegacyDatasourceReader obj's underlying member method code with example usage: obj.estimate_inmemory_data_size() and returns: None