code: def _add_scanvec(self, mutinfo):
          
          vb, uuid, seq, bktname = mutinfo
          self._sv.setdefault(bktname, {})[vb] = (seq, str(uuid))
docs: Internal method used to specify a scan vector.
          :param mutinfo: A tuple in the form of
              `(vbucket id, vbucket uuid, mutation sequence)`