code: def index(self):
      return getattr(self, "_index", None)
  
file_path: mars/mars/core/entity/chunks.py
imports: from ...serialization.serializables import BoolField, FieldTypes, TupleField
  from ...utils import tokenize
  from .core import EntityData, Entity
label_desc: Use image node_id 2 for calling the ChunkData obj's underlying member method code with example usage: obj.index() and returns: getattr