'Add or remove consistency group members
:param es_cg: The E-Series consistency group
:param add_volumes: A list of Cinder volumes to add to the
consistency group
:param remove_volumes: A list of Cinder volumes to remove from the
consistency group
:return: None'

def _update_consistency_group_members(self, es_cg, add_volumes, remove_volumes):

    for volume in remove_volumes:
        es_vol = self._get_volume(volume['id'])
        LOG.info('Removing    volume    %(v)s    from    consistency    group    %(cg)s.', {'v': es_vol['label'], 'cg': es_cg['label']})
        self._client.remove_consistency_group_member(es_vol['id'], es_cg['id'])
    for volume in add_volumes:
        es_vol = self._get_volume(volume['id'])
        LOG.info('Adding    volume    %(v)s    to    consistency    group    %(cg)s.', {'v': es_vol['label'], 'cg': es_cg['label']})
        self._client.add_consistency_group_member(es_vol['id'], es_cg['id'])
