def InvalidParsedHotlistRefsNames(parsed_hotlist_refs, user_hotlist_pbs):
  """Find and return all names without a corresponding hotlist so named.

  Args:
    parsed_hotlist_refs: a list of ParsedHotlistRef objects
    user_hotlist_pbs: the hotlist protobuf objects of all hotlists
      belonging to the user

  Returns:
    a list of invalid names; if none are found, the empty list
  """
  user_hotlist_names = {hotlist.name for hotlist in user_hotlist_pbs}
  invalid_names = list()
  for parsed_ref in parsed_hotlist_refs:
    if parsed_ref.hotlist_name not in user_hotlist_names:
      invalid_names.append(parsed_ref.hotlist_name)
  return invalid_names