code: def shard_id(self) -> int:
      return self._shard_id
  
file_path: mars/mars/dataframe/contrib/raydataset/mldataset.py
imports: import numpy
  import pandas
  from collections import defaultdict
  from typing import Dict, Iterable, List, Tuple
  from ....utils import lazy_import
label_desc: Use image node_id 2 for calling the ChunkRefBatch obj's underlying member method code with example usage: obj.shard_id() and returns: self