code: def add_observers(self, observers: List[Observer]):
      for observer in observers:
          self.add_observer(observer)
      return self
  
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 4 for calling the ObservableMixin obj's underlying member method code with example usage: obj.add_observers(observers) and returns: self