class_docstr: A MapTransformFn that converts input blocks to batches.
class_docstr_tok: ["A","MapTransformFn","that","converts","input","blocks","to","batches","."]
code: def batch_size(self) -> Optional[int]:
      return self._batch_size
  
imports: import itertools
  from abc import abstractmethod
  from enum import Enum
  from typing import Any, Callable, Dict, Iterable, List, Optional, TypeVar, Union
  from ray.data._internal.block_batching.block_batching import batch_blocks
  from ray.data._internal.execution.interfaces.task_context import TaskContext
  from ray.data._internal.output_buffer import BlockOutputBuffer
  from ray.data.block import Block, BlockAccessor, DataBatch
label_desc: Use image node_id 3 for calling the BlocksToBatchesMapTransformFn obj's underlying member method code with example usage: obj.batch_size() and returns: self