<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _FormatMessages(self, format_string, short_format_string, event_values):
 """Determines the formatted message strings. Args: format_string (str):
 message format string. short_format_string (str):
 short message format string. event_values (dict[str, object]):
 event values. Returns: tuple(str, str):
 formatted message string and short message string. """

    message_string = self._FormatMessage(format_string, event_values)

    if short_format_string:
      short_message_string = self._FormatMessage(
          short_format_string, event_values)
    else:
      short_message_string = message_string

    # Truncate the short message string if necessary.
    if len(short_message_string) > 80:
      short_message_string = '{0:s}...'.format(short_message_string[:77])

    return message_string, short_message_string