code: def _observable_value_types(self) -> Dict[str, Type]:
      raise NotImplementedError
  
file_path: ReAgent/reagent/core/tracker.py
imports: import functools
  import logging
  from typing import Dict, List, Type
  import torch
label_desc: Use image node_id 2 for calling the ObservableMixin obj's underlying member method code with example usage: obj._observable_value_types() without return types