code: def _CopyFromDateTimeString(self, time_string):
      
      date_time_values = self._CopyDateTimeFromString(time_string)
  
      year = date_time_values.get('year', 0)
      month = date_time_values.get('month', 0)
      day_of_month = date_time_values.get('day_of_month', 0)
      hours = date_time_values.get('hours', 0)
      minutes = date_time_values.get('minutes', 0)
      seconds = date_time_values.get('seconds', 0)
      microseconds = date_time_values.get('microseconds', None)
  
      timestamp = self._GetNumberOfSecondsFromElements(
          year, month, day_of_month, hours, minutes, seconds)
      timestamp *= definitions.NANOSECONDS_PER_SECOND
  
      if microseconds:
        nanoseconds = microseconds * definitions.MILLISECONDS_PER_SECOND
        timestamp += nanoseconds
  
      self._normalized_timestamp = None
      self._timestamp = timestamp
docs: Copies a POSIX timestamp from a date and time string.
  
      Args:
        time_string (str): date and time value formatted as:
            YYYY-MM-DD hh:mm:ss.######[+-]##:##
  
            Where # are numeric digits ranging from 0 to 9 and the seconds
            fraction can be either 3 or 6 digits. The time of day, seconds
            fraction and time zone offset are optional. The default time zone
            is UTC.