code: def get_timestamp(self, url, xpath=None):
          
          if not path.exists(self.db_path):
              return None
  
          if self._query(url, xpath).count() > 0:
              return self._query(url, xpath).one().queried_on
docs: Get time stamp of cached query result.
  
          If DB has not yet been initialized or url/xpath has not been queried yet, return None.
  
          Args:
              url (str): If given, clear specific item only. Otherwise remove the DB file.
              xpath (str): xpath to search (may be ``None``)
  
          Returns:
              datetime.datetime: cached response timestamp, None if not available