docs: def create(self, volume_id, vtype, size, affinity):
          """
          create a volume
          """
          volume_id = volume_id or str(uuid.uuid4())
          params = {'volume_type_name': vtype,
                    'size': size,
                    'affinity': affinity}
          return self.http_put('/volumes/%s' % volume_id,
                               params=self.unused(params))