class_docstr: Simple observer that collect values into a list
class_docstr_tok: ["Simple","observer","that","collect","values","into","a","list"]
code: def update(self, key: str, value):
      self.values.append(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 ValueListObserver obj's underlying member method code with example usage: obj.update(key, value) without return types