title: NLTK Example for Relation Extraction Does not work
body: <p>I have gotten through parts of the nltk book until this section on relation extracting. Can someone help me understand why the code below does not work? There does not seem to be the method show_raw_rtuple()</p>
  
  <pre><code>IN = re.compile(r'.*\bin\b(?!\b.+ing)')
  for doc in nltk.corpus.ieer.parsed_docs('NYT_19980315'):
      for rel in nltk.sem.extract_rels('ORG', 'LOC', doc,
                                      corpus='ieer', pattern = IN):
          print nltk.sem.show_raw_rtuple(rel)
  </code></pre>