class_docstr: A builder class for blocks.
class_docstr_tok: ["A","builder","class","for","blocks","."]
docstr: Return the number of rows added in the block.
docstr_tok: ["Return","the","number","of","rows","added","in","the","block","."]
code: def num_rows(self) -> int:
      """Return the number of rows added in the block."""
      raise NotImplementedError
  
file_path: ray/python/ray/data/_internal/block_builder.py
imports: from typing import Generic
  from ray.data.block import Block, BlockAccessor, T
label_desc: Use image node_id 6 for calling the BlockBuilder obj's underlying member method code with example usage: obj.num_rows() without return types