code: def attach_to_instance(self, instance, mountpoint):
          
          instance_id = _resolve_id(instance)
          try:
              resp = self._nova_volumes.create_server_volume(instance_id,
                      self.id, mountpoint)
          except Exception as e:
              raise exc.VolumeAttachmentFailed("%s" % e)
docs: Attaches this volume to the cloud server instance at the
          specified mountpoint. This requires a call to the cloud servers
          API; it cannot be done directly.