code: def get_high_water_mark(self, mark_type, obstory_name=None):
          
          if obstory_name is None:
              obstory_name = self.obstory_name
  
          obstory = self.get_obstory_from_name(obstory_name)
          key_id = self.get_hwm_key_id(mark_type)
  
          self.con.execute('SELECT time FROM archive_highWaterMarks WHERE markType=%s AND observatoryId=%s',
                           (key_id, obstory['uid']))
          results = self.con.fetchall()
          if len(results) > 0:
              return results[0]['time']
          return None
docs: Retrieves the high water mark for a given obstory, defaulting to the current installation ID
  
          :param string mark_type:
              The type of high water mark to set
          :param string obstory_name:
              The obstory ID to check for, or the default installation ID if not specified
          :return:
              A UTC datetime for the high water mark, or None if none was found.