rdflib issue wirh nested references

I am looking at this code:

from rdflib import URIRef, BNode, Literal
import rdflib

bob = URIRef("http://ift.tt/1uyaLu3")
linda = BNode()

name = Literal('Bob') # passing a string
age = Literal(24) # passing a python int
height = Literal(76.5) # passing a python float
from rdflib import Namespace

n = Namespace("http://ift.tt/1uyaLKj")
from rdflib.namespace import RDF, FOAF

from rdflib import Graph
g = Graph()

g.add( (bob, RDF.type, FOAF.Person) )
g.add( (bob, FOAF.name, name) )
g.add( (bob, FOAF.knows, linda) )
g.add( (linda, RDF.type, FOAF.Person) )
g.add( (linda, FOAF.name, Literal('Linda') ) )

g.serialize("prova.rdf",format="pretty-xml")

When I open the file i have this output:

<?xml version="1.0" encoding="utf-8"?>
<rdf:RDF
  xmlns:ns1="http://ift.tt/PpfGLc"
  xmlns:rdf="http://ift.tt/oZyhLL"
>
  <ns1:Person rdf:about="http://ift.tt/1uyaLu3">
    <ns1:name>Bob</ns1:name>
    <ns1:knows>
      <ns1:Person rdf:nodeID="N85c01d2d7fd54f8395c75906f5bdc93f">
        <ns1:name>Linda</ns1:name>
      </ns1:Person>
    </ns1:knows>
  </ns1:Person>
</rdf:RDF>

As you can see, in the "knows" sector, i see the details of the linked node (Linda). I would expect something like this:

<?xml version="1.0" encoding="utf-8"?>
<rdf:RDF
  xmlns:ns1="http://ift.tt/PpfGLc"
  xmlns:rdf="http://ift.tt/oZyhLL"> 

 <ns1:Person rdf:about="http://ift.tt/1uyaLu3">
    <ns1:name>Bob</ns1:name>
    <ns1:knows  rdf:nodeID="N85c01d2d7fd54f8395c75906f5bdc93f"/>
    </ns1:Person>
    <ns1:Person rdf:nodeID="N85c01d2d7fd54f8395c75906f5bdc93f">
    <ns1:name>Linda</ns1:name>
    </ns1:Person>
</rdf:RDF>

How can I get this kind of output? In particular I would like to see only the reference of Linda in the Bob ns1:knows list. Any suggestion? Where am I wrong?