docs: def get_mor(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))