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: graph_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©2022 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"
	"io"
	"log"
	"os"
	"strings"

	"gonum.org/v1/gonum/graph/formats/rdf"
)

func ExampleGraph() {
	f, err := os.Open("path/to/graph.nq")
	if err != nil {
		log.Fatal(err)
	}

	dec := rdf.NewDecoder(f)
	var statements []*rdf.Statement
	for {
		s, err := dec.Unmarshal()
		if err != nil {
			if err != io.EOF {
				log.Fatalf("error during decoding: %v", err)
			}
			break
		}

		// Statements can be filtered at this point to exclude unwanted
		// or irrelevant parts of the graph.
		statements = append(statements, s)
	}
	f.Close()

	// Canonicalize blank nodes to reduce memory footprint.
	statements, err = rdf.URDNA2015(statements, statements)
	if err != nil {
		log.Fatal(err)
	}

	g := rdf.NewGraph()
	for _, s := range statements {
		g.AddStatement(s)
	}

	// Do something with the graph.
}

const gods = `
_:alcmene <l:type> "human" .
_:alcmene <p:name> "Alcmene" .
_:cerberus <a:lives> _:cerberushome .
_:cerberus <l:type> "monster" .
_:cerberus <p:name> "Cerberus" .
_:cerberushome <p:location> _:tartarus .
_:cronos <l:type> "titan" .
_:cronos <p:name> "Cronos" .
_:hades <a:lives> _:hadeshome .
_:hades <h:brother> _:poseidon .
_:hades <h:brother> _:zeus .
_:hades <h:pet> _:cerberus .
_:hades <l:type> "god" .
_:hades <p:name> "Hades" .
_:hadeshome <p:location> _:tartarus .
_:hadeshome <p:reason> "it is peaceful" .
_:heracles <a:battled> _:cerberus .
_:heracles <a:battled> _:hydra .
_:heracles <a:battled> _:nemean .
_:heracles <h:father> _:zeus .
_:heracles <h:mother> _:alcmene .
_:heracles <l:type> "demigod" .
_:heracles <p:name> "Heracles" .
_:hydra <l:type> "monster" .
_:hydra <p:name> "Lernean Hydra" .
_:nemean <l:type> "monster" .
_:nemean <p:name> "Nemean Lion" .
_:olympus <l:type> "location" .
_:olympus <p:name> "Olympus" .
_:poseidon <a:lives> _:poseidonhome .
_:poseidon <h:brother> _:hades .
_:poseidon <h:brother> _:zeus .
_:poseidon <l:type> "god" .
_:poseidon <p:name> "Poseidon" .
_:poseidonhome <p:location> _:sea .
_:poseidonhome <p:reason> "it was given to him" .
_:sea <l:type> "location" .
_:sea <p:name> "Sea" .
_:tartarus <l:type> "location" .
_:tartarus <p:name> "Tartarus" .
_:theseus <a:battled> _:cerberus .
_:theseus <h:father> _:poseidon .
_:theseus <l:type> "human" .
_:theseus <p:name> "Theseus" .
_:zeus <a:lives> _:zeushome .
_:zeus <h:brother> _:hades .
_:zeus <h:brother> _:poseidon .
_:zeus <h:father> _:cronos .
_:zeus <l:type> "god" .
_:zeus <p:name> "Zeus" .
_:zeushome <p:location> _:olympus .
_:zeushome <p:reason> "he can see everything" .
`

func ExampleQuery() {
	g := rdf.NewGraph()
	dec := rdf.NewDecoder(strings.NewReader(gods))
	for {
		s, err := dec.Unmarshal()
		if err != nil {
			if err != io.EOF {
				log.Fatalf("error during decoding: %v", err)
			}
			break
		}
		g.AddStatement(s)
	}

	it := g.Nodes()
	nodes := make([]rdf.Term, 0, it.Len())
	for it.Next() {
		nodes = append(nodes, it.Node().(rdf.Term))
	}

	// Construct a query start point. This can be reused. If a specific
	// node is already known it can be used to reduce the work required here.
	heracles := g.Query(nodes...).In(func(s *rdf.Statement) bool {
		// Traverse in from the name "Heracles".
		return s.Predicate.Value == "<p:name>" && s.Object.Value == `"Heracles"`
	})

	// father and name filter statements on their predicate values. These
	// are used in the queries that follow.
	father := func(s *rdf.Statement) bool {
		// Traverse across <h:father>.
		return s.Predicate.Value == "<h:father>"
	}
	name := func(s *rdf.Statement) bool {
		// Tr
    
func ExampleQuery() {
	g := rdf.NewGraph()
	dec := rdf.NewDecoder(strings.NewReader(gods))
	for {
		s, err := dec.Unmarshal()
		if err != nil {
			if err != io.EOF {
				log.Fatalf("error during decoding: %v", err)
			}
			break
		}
		g.AddStatement(s)
	}

	it := g.Nodes()
	nodes := make([]rdf.Term, 0, it.Len())
	for it.Next() {
		nodes = append(nodes, it.Node().(rdf.Term))
	}

	// Construct a query start point. This can be reused. If a specific
	// node is already known it can be used to reduce the work required here.
	heracles := g.Query(nodes...).In(func(s *rdf.Statement) bool {
		// Traverse in from the name "Heracles".
		return s.Predicate.Value == "<p:name>" && s.Object.Value == `"Heracles"`
	})

	// father and name filter statements on their predicate values. These
	// are used in the queries that follow.
	father := func(s *rdf.Statement) bool {
		// Traverse across <h:father>.
		return s.Predicate.Value == "<h:father>"
	}
	name := func(s *rdf.Statement) bool {
		// Traverse across <p:name>.
		return s.Predicate.Value == "<p:name>"
	}

	// g.V().has('name', 'heracles').out('father').out('father').values('name')
	for _, r := range heracles.
		Out(father). // Traverse out across <h:father> to get to Zeus.
		Out(father). // and again to get to Cronos.
		Out(name).   // Retrieve the name by traversing the <p:name> edges.
		Result() {
		fmt.Printf("Heracles' grandfather: %s\n", r.Value)
	}

	// g.V().has('name', 'heracles').repeat(out('father')).emit().values('name')
	var i int
	heracles.Repeat(func(q rdf.Query) (rdf.Query, bool) {
		q = q.Out(father)
		for _, r := range q.Out(name).Result() {
			fmt.Printf("Heracles' lineage %d: %s\n", i, r.Value)
		}
		i++
		return q, true
	})

	// parents and typ are helper filters for queries below.
	parents := func(s *rdf.Statement) bool {
		// Traverse across <h:father> or <h:mother>
		return s.Predicate.Value == "<h:father>" || s.Predicate.Value == "<h:mother>"
	}
	typ := func(s *rdf.Statement) bool {
		// Traverse across <l:type>.
		return s.Predicate.Value == "<l:type>"
	}

	// g.V(heracles).out('father', 'mother').label()
	for _, r := range heracles.Out(parents).Out(typ).Result() {
		fmt.Printf("Heracles' parents' types: %s\n", r.Value)
	}

	// battled is a helper filter for queries below.
	battled := func(s *rdf.Statement) bool {
		// Traverse across <a:battled>.
		return s.Predicate.Value == "<a:battled>"
	}

	// g.V(heracles).out('battled').label()
	for _, r := range heracles.Out(battled).Out(typ).Result() {
		fmt.Printf("Heracles' antagonists' types: %s\n", r.Value)
	}

	// g.V(heracles).out('battled').valueMap()
	for _, r := range heracles.Out(battled).Result() {
		m := make(map[string]string)
		g.Query(r).Out(func(s *rdf.Statement) bool {
			// Store any p: namespace in the map.
			if strings.HasPrefix(s.Predicate.Value, "<p:") {
				prop := strings.TrimSuffix(strings.TrimPrefix(s.Predicate.Value, "<p:"), ">")
				m[prop] = s.Object.Value
			}
			// But don't store the result into the query.
			return false
		})
		fmt.Println(m)
	}

	// g.V(heracles).as('h').out('battled').in('battled').where(neq('h')).values('name')
	for _, r := range heracles.Out(battled).In(battled).Not(heracles).Out(name).Result() {
		fmt.Printf("Heracles' allies: %s\n", r.Value)
	}

	// Construct a query start point for Hades, this time using a restricted
	// starting set only including the name. It would also be possible to
	// start directly from a query with the term _:hades, but that depends
	// on the blank node identity, which may be altered, for example by
	// canonicalization.
	h, ok := g.TermFor(`"Hades"`)
	if !ok {
		log.Fatal("could not find term for Hades")
	}
	hades := g.Query(h).In(name)

	// g.V(hades).as('x').out('lives').in('lives').where(neq('x')).values('name')
	//
	// This is more complex with RDF since properties are encoded by
	// attachment to anonymous blank nodes, so we take two steps, the
	// first to the blank node for where Hades lives and then the second
	// to get the actual location.
	lives := func(s *rdf.Statement) bool {
		// Traverse across <a:lives>.
		return s.Predicate.Value == "<a:lives>"
	}
	location := func(s *rdf.Statement) bool {
		// Traverse across <p:location>.
		return s.Predicate.Value == "<p:location>"
	}
	for _, r := range hades.Out(lives).Out(location).In(location).In(lives).Not(hades).Out(name).Result() {
		fmt.Printf("Hades lives with: %s\n", r.Value)
	}

	// g.V(hades).out('brother').as('god').out('lives').as('place').select('god', 'place').by('name')
	brother := func(s *rdf.Statement) bool {
		// Traverse across <h:brother>.
		return s.Predicate.Value == "<h:brother>"
	}
	for _, r := range hades.Out(brother).Result() {
		m := make(map[string]string)
		as := func(key string) func(s *rdf.Statement) bool {
			return func(s *rdf.Statement) bool {
				// Store any <p:name> objects in the map.
				if s.Predicate.Value == "<p:name>" {
					m[key] = s.Object.Value
				}
				// But don't store the result into the query.
				return false
			}
		}
		sub := g.Query(r)
		sub.Out(as("god"))
		sub.Out(lives).Out(location).Out(as("place"))
		fmt.Println(m)
	}

	// The query above but with the reason for their choice.
	for _, r := range hades.Out(brother).Result() {
		m := make(map[string]string)
		// as stores the query result under the provided key
		// for m, and if cont is not nil, allows the chain
		// to continue.
		as := func(query, key string, cont func(s *rdf.Statement) bool) func(s *rdf.Statement) bool {
			return func(s *rdf.Statement) bool {
				// Store any objects matching the query in the map.
				if s.Predicate.Value == query {
					m[key] = s.Object.Value
				}
				// Continue with chain if cont is not nil and
				// the statement satisfies its condition.
				if cont == nil {
					return false
				}
				return cont(s)
			}
		}
		sub := g.Query(r)
		sub.Out(as("<p:name>", "god", nil))
		sub.Out(lives).
			Out(as("<p:reason>", "reason", location)).
			Out(as("<p:name>", "place", nil))
		fmt.Println(m)
	}

	// Unordered output:
	//
	// Heracles' grandfather: "Cronos"
	// Heracles' lineage 0: "Zeus"
	// Heracles' lineage 1: "Cronos"
	// Heracles' parents' types: "god"
	// Heracles' parents' types: "human"
	// Heracles' antagonists' types: "monster"
	// Heracles' antagonists' types: "monster"
	// Heracles' antagonists' types: "monster"
	// map[name:"Cerberus"]
	// map[name:"Lernean Hydra"]
	// map[name:"Nemean Lion"]
	// Heracles' allies: "Theseus"
	// Hades lives with: "Cerberus"
	// map[god:"Zeus" place:"Olympus"]
	// map[god:"Poseidon" place:"Sea"]
	// map[god:"Zeus" place:"Olympus" reason:"he can see everything"]
	// map[god:"Poseidon" place:"Sea" reason:"it was given to him"]
}