code: def unregister_fetcher(self, object_class):
          
          self._lock.acquire()
          try:
              cache = self._caches.get(object_class)
              if not cache:
                  return
              cache.set_fetcher(None)
          finally:
              self._lock.release()
docs: Unregister a fetcher class for an object class.
  
          :Parameters:
              - `object_class`: class retrieved by the fetcher.
          :Types:
              - `object_class`: `classobj`