You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: rdf_line_example_test.go
    path of file: ./repos/gonum/graph/formats/rdf
    
    the code of the file until where you have to start completion: // Copyright Â©2020 The Gonum Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package rdf_test

import (
	"fmt"
	"log"
	"strings"

	"gonum.org/v1/gonum/graph"
	"gonum.org/v1/gonum/graph/en
    
func (n foodNode) DOTID() string {
	text, _, kind, err := n.Term.Parts()
	if err != nil {
		return fmt.Sprintf("error:%s", n.Term.Value)
	}
	switch kind {
	case rdf.Blank:
		return n.Term.Value
	case rdf.IRI:
		return text
	case rdf.Literal:
		return fmt.Sprintf("%q", text)
	default:
		return fmt.Sprintf("invalid:%s", n.Term.Value)
	}
}