code: def _update_key(self):
      object.__setattr__(
          self,
          "_key",
          tokenize(
              type(self).__name__,
              *(
                  getattr(self, k, None)
                  for k in self._keys_
                  if k != "_index"
              ),
          ),
      )
  
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 4 for calling the ChunkData obj's underlying member method code with example usage: obj._update_key() without return types