Fixed method to check if an object is first level in objectdb.

        '''

        ids = set()

        for oid in self._objects:

            parid = oid.partition('.')[0]

            ids.add(parid)

        for obj in self._objects.values():

            if not '__parent' in obj:

                ids.add(obj['id'])

        return ids

    def get(self, oid):