docs: def datetime_to_str(date_time=None, str_format='%Y-%m-%d_%H:%M:%S.fff'):
      """
      :param   date_time: datetime of the date to convert to string
      :param   str_format: str of the format to return the string in
      :return: str of the timestamp
      """
      date_time = date_time or cst_now()
      if DEFAULT_TIMEZONE_AWARE:
          date_time += timedelta(hours=DEFAULT_TIMEZONE)
      ret = date_time.strftime(str_format.split('.f')[0])
      if '.f' in str_format:
          sig_digits = len(str_format.split('.')[-1]) + 1
          ret += str(date_time.microsecond / 1000000.0
                     )[1:].ljust(sig_digits, '0')[:sig_digits]
      return ret