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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _FormatDescription(self, event):
 """Formats the description. Args: event (EventObject):
 event. Returns: str: formatted description field. """

    date_time_string = timelib.Timestamp.CopyToIsoFormat(
        event.timestamp, timezone=self._output_mediator.timezone)
    timestamp_description = event.timestamp_desc or 'UNKNOWN'

    message, _ = self._output_mediator.GetFormattedMessages(event)
    if message is None:
      data_type = getattr(event, 'data_type', 'UNKNOWN')
      raise errors.NoFormatterFound(
          'Unable to find event formatter for: {0:s}.'.format(data_type))

    description = '{0:s}; {1:s}; {2:s}'.format(
        date_time_string, timestamp_description,
        message.replace(self._DESCRIPTION_FIELD_DELIMITER, ' '))
    return self._SanitizeField(description)