code: func (node *PathExpression) Part(part string) {
  	node.Original += part
  
  	switch part {
  	case "..":
  		node.Depth++
  		node.Scoped = true
  	case ".", "this":
  		node.Scoped = true
  	default:
  		node.Parts = append(node.Parts, part)
  	}
  }
docs: // Part adds path part.