code: def set_item(self, key, url):
          
          if self._db.search(self._urls.key == key):
              self._db.update({'url': url}, self._urls.key == key)
          else:
              self._db.insert({'key': key, 'url': url})
docs: Store the url value under the unique key.
  
          :Args:
              - key[str]: The unique id to which the item (in this case, url) would be stored.
              - value[str]: The actual url value to be stored.