class_docstr: A bound read operation for a :class:`~ray.data.Datasource`.
  
  This is a stateful class so that reads can be prepared in multiple stages.
  For example, it is useful for :class:`Datasets <ray.data.Dataset>` to know the
  in-memory size of the read prior to executing it.
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docstr: Return an estimate of the in-memory data size, or None if unknown.
  
  Note that the in-memory data size may be larger than the on-disk data size.
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code: def estimate_inmemory_data_size(self) -> Optional[int]:
      """Return an estimate of the in-memory data size, or None if unknown.
  
      Note that the in-memory data size may be larger than the on-disk data size.
      """
      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 1 for calling the Reader obj's underlying member method code with example usage: obj.estimate_inmemory_data_size() without return types