def unregister_fetcher(self, object_class):
self._lock.acquire()<EOL>try:<EOL><INDENT>cache = self._caches.get(object_class)<EOL>if not cache:<EOL><INDENT>return<EOL><DEDENT>cache.set_fetcher(None)<EOL><DEDENT>finally:<EOL><INDENT>self._lock.release()<EOL><DEDENT>
Unregister a fetcher class for an object class.

        :Parameters:
            - `object_class`: class retrieved by the fetcher.
        :Types:
            - `object_class`: `classobj`