'Update metadata for specific volume
http://localhost/api/cinder/volumetypes/1/metadata'

@rest_utils.ajax()
def patch(self, request, volume_type_id):

    updated = request.DATA['updated']
    removed = request.DATA['removed']
    if updated:
        api.cinder.volume_type_extra_set(request, volume_type_id, updated)
    if removed:
        api.cinder.volume_type_extra_delete(request, volume_type_id, removed)
