title: How to add rdflib plugin (rdflib.serializer.Serializer) in python (jupyter notebook)
body: <p>I am working with RDF and using rdflib in python. Able to read, subject predicate and object but when tried to view in turtle format its giving plugin error.</p>
  <pre><code>#pip install rdflib
  #pip show rdflib
  
  from rdflib import Graph
  
  # Intializing Graph
  g = Graph()
  
  # Parse in a RDF file graph dbpedia
  g.parse('http://dbpedia.org/resource/Michael_Jackson')
  
  # Loop through  each triplet in graph (subj, pred, obj)
  for index, (sub, pred, obj) in enumerate(g):
      print(sub, pred, obj)
      if index == 10:
          break
  
  #print entire graph in RDF turtle format
  print(g.serialize(format='tt1').decode('u8'))
  </code></pre>
  <p>For the last command I am getting error as :</p>
  <pre><code>---------------------------------------------------------------------------
  
  PluginException: No plugin registered for (tt1, &lt;class 'rdflib.serializer.Serializer'&gt;)
  </code></pre>