class_docstr: Simple observer that collect values into a list
class_docstr_tok: ["Simple","observer","that","collect","values","into","a","list"]
code: def __init__(self, observing_key: str):
      super().__init__(observing_keys=[observing_key])
      self.observing_key = observing_key
      self.values: List[Any] = []
  
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 1 to create a new ValueListObserver object from inherited base classes: Observer with example: obj = ValueListObserver(observing_key)