code: func (e *executor) executeShiftShard(ctx context.Context, index string, c *pql.Call, shard uint64) (*Row, error) {
  	n, _, err := c.IntArg("n")
  	if err != nil {
  		return nil, fmt.Errorf("executeShiftShard: %v", err)
  	}
  
  	if len(c.Children) == 0 {
  		return nil, errors.New("Shift() requires an input row")
  	} else if len(c.Children) > 1 {
  		return nil, errors.New("Shift() only accepts a single row input")
  	}
  
  	row, err := e.executeBitmapCallShard(ctx, index, c.Children[0], shard)
  	if err != nil {
  		return nil, err
  	}
  
  	return row.Shift(n)
  }
docs: // executeShiftShard executes a shift() call for a local shard.