class_docstr: A composite observer which takes care of dispatching values to child observers
class_docstr_tok: ["A","composite","observer","which","takes","care","of","dispatching","values","to","child","observers"]
code: def update(self, key: str, value):
      for observer in self.observers[key]:
          observer.update(key, value)
  
imports: import logging
  from typing import Any, Dict, Iterable, List, Optional
  from reagent.core.tensorboardX import SummaryWriterContext
  from reagent.core.tracker import Aggregator, Observer
label_desc: Use image node_id 2 for calling the CompositeObserver obj's underlying member method code with example usage: obj.update(key, value) without return types