title: NLTK ValueError: too many values to unpack (expected 2)
body: <p>I should train the model to determine gender of a name.
  I made the list like </p>
  
  <blockquote>
    <p>[['Friedtic', 'Homer'], ['Alice', 'Miranda']]</p>
  </blockquote>
  
  <p>I tried </p>
  
  <pre><code>classifier = nltk.NaiveBayesClassifier.train(train_data)
  </code></pre>
  
  <p>but there is the error</p>
  
  <blockquote>
    <p>ValueError: too many values to unpack (expected 2)</p>
  </blockquote>