code: def _GetNormalizedTimestamp(self):
      
      if self._normalized_timestamp is None:
        if (self._timestamp is not None and self._timestamp >= self._INT64_MIN and
            self._timestamp <= self._INT64_MAX):
          self._normalized_timestamp = (
              decimal.Decimal(self._timestamp) /
              definitions.MICROSECONDS_PER_SECOND)
          self._normalized_timestamp -= self._WEBKIT_TO_POSIX_BASE
  
      return self._normalized_timestamp
docs: Retrieves the normalized timestamp.
  
      Returns:
        float: normalized timestamp, which contains the number of seconds since
            January 1, 1970 00:00:00 and a fraction of second used for increased
            precision, or None if the normalized timestamp cannot be determined.