def CopyToDateTimeString(self):
if self._number_of_seconds is None or self.fraction_of_second is None:<EOL><INDENT>return None<EOL><DEDENT>precision_helper = precisions.PrecisionHelperFactory.CreatePrecisionHelper(<EOL>self._precision)<EOL>return precision_helper.CopyToDateTimeString(<EOL>self._time_elements_tuple, self.fraction_of_second)<EOL>
Copies the time elements to a date and time string.

        Returns:
          str: date and time value formatted as: "YYYY-MM-DD hh:mm:ss" or
              "YYYY-MM-DD hh:mm:ss.######" or None if time elements are missing.

        Raises:
          ValueError: if the precision value is unsupported.