code: def _from_string(cls, serialized):
          
          parse = cls.parse_url(serialized)
  
          if parse['version_guid']:
              parse['version_guid'] = cls.as_object_id(parse['version_guid'])
  
          return cls(**{key: parse.get(key) for key in cls.KEY_FIELDS})
docs: Return a CourseLocator parsing the given serialized string
          :param serialized: matches the string to a CourseLocator