code: def _from_string(cls, serialized):
          
          parse = cls.URL_RE.match(serialized)
          if not parse:
              raise InvalidKeyError(cls, serialized)
  
          parse = parse.groupdict()
          if parse['definition_id']:
              parse['definition_id'] = cls.as_object_id(parse['definition_id'])
  
          return cls(**{key: parse.get(key) for key in cls.KEY_FIELDS})
docs: Return a DefinitionLocator parsing the given serialized string
          :param serialized: matches the string to