def _fill_zero_counters_dict(counters_config, counters_dict):
  """ A util function for filling counters dict with all counters set to 0.

  Args:
    counters_config: a tuple containing cumulative counters configuration.
    counters_dict: an empty dict to fill with zero counters.
  Returns:
    a filled dictionary with zero counters.
  """
  for counter_name, categorizer, _, _ in counters_config:
    # Counters config can contain following types of items:
      #  - str, None, callable(summarizer), None
      #  - str, callable(categorizer), callable(summarizer), None
      #  - str, callable(categorizer), None, nested config(tuple)
    if categorizer is None:
      # Set single counter if key is str
      counters_dict[counter_name] = 0
    else:
      # if categorizer
      counters_dict[counter_name] = {}
  return counters_dict