code: def dict_of_lists_add(dictionary, key, value):
      # type: (DictUpperBound, Any, Any) -> None
      
      list_objs = dictionary.get(key, list())
      list_objs.append(value)
      dictionary[key] = list_objs
docs: Add value to a list in a dictionary by key
  
      Args:
          dictionary (DictUpperBound): Dictionary to which to add values
          key (Any): Key within dictionary
          value (Any): Value to add to list in dictionary
  
      Returns:
          None