如何在RDFLib中向图表添加注释或标签？

URIRef

<http://data.org/inst1> <http://xmlns.com/foaf/0.1/name> "david" .
<http://data.org/inst2> <http://xmlns.com/foaf/0.1/name> "luis" .
<http://data.org/inst3> <http://xmlns.com/foaf/0.1/name> "max" .

<http://data.org/inst1> <http://xmlns.com/foaf/0.1/knows> <http://data.org/inst2> .
<http://data.org/inst2> <http://xmlns.com/foaf/0.1/knows> <http://data.org/inst3> .
<http://data.org/inst3> <http://xmlns.com/foaf/0.1/knows> <http://data.org/inst1> .

import rdflib

g = rdflib.ConjunctiveGraph("IOMemory",)

#g is made of two sub-graphs or triples gathered in two different contexts.
#the second paramaters identifies the URIRef for each subgraph.
g.parse("dataA.nt",rdflib.URIRef("http://mygraphs.org/names"),format="n3")
g.parse("dataB.nt",rdflib.URIRef("http://mygraphs.org/relations"),format="n3")

print "traverse all contexts and all triples for each context"
for subgraph in g.contexts():
    print "Graph name",subgraph.identifier 
    for triple in subgraph.triples((None,None,None)):
        print triple

print "traverse all contexts where a triple appears"
for subgraph in g.contexts(triple=(rdflib.URIRef('http://data.org/inst1'),rdflib.URIRef("http://xmlns.com/foaf/0.1/name"),rdflib.Literal(u'david'))):
    print "Graph name",subgraph.identifier 
    for triple in subgraph.triples((None,None,None)):
        print triple

print "traverse a triple pattern regardless the context is in"
for t in g.triples((None,rdflib.URIRef("http://xmlns.com/foaf/0.1/name"),None)):
    print t