def METHOD_NAME(self, key, name):
    """
    Return the Mor object identified by `name` for the given instance key.
    If the key is not in the cache, raises a KeyError.
    If there's no Mor with the given name, raises a MorNotFoundError.
    """
    with self._mor_lock:
        mors = self._mor[key]
        try:
            return mors[name]
        except KeyError:
            raise MorNotFoundError("Mor object '{}' is not in the cache.".format(name))