code: func (s *tikvSnapshot) Get(k kv.Key) ([]byte, error) {
  	ctx := context.WithValue(context.Background(), txnStartKey, s.version.Ver)
  	val, err := s.get(NewBackoffer(ctx, getMaxBackoff), k)
  	if err != nil {
  		return nil, errors.Trace(err)
  	}
  	if len(val) == 0 {
  		return nil, kv.ErrNotExist
  	}
  	return val, nil
  }
docs: // Get gets the value for key k from snapshot.