code: func (n *PrivElem) Accept(v Visitor) (Node, bool) {
  	newNode, skipChildren := v.Enter(n)
  	if skipChildren {
  		return v.Leave(newNode)
  	}
  	n = newNode.(*PrivElem)
  	for i, val := range n.Cols {
  		node, ok := val.Accept(v)
  		if !ok {
  			return n, false
  		}
  		n.Cols[i] = node.(*ColumnName)
  	}
  	return v.Leave(n)
  }
docs: // Accept implements Node Accept interface.