title: tensorflow.contrib.learn.DNNclassifier missing 1 required positional argument: 'feature_columns'
body: <p>I'm using jupyter notebook to write a deep neural network code. I've encountered this problem when trying to create a DNNClassifier.</p>
  
  <pre><code>import tensorflow.contrib.learn as learn
  classifier = learn.DNNClassifier(hidden_units=[10, 20, 10], n_classes=2)
  
  ---------------------------------------------------------------------------
  TypeError                                 Traceback (most recent call last)
  &lt;ipython-input-30-0273d6847e2b&gt; in &lt;module&gt;()
  ----&gt; 1 classifier = learn.DNNClassifier(hidden_units=[10, 20, 10], n_classes=2)
  
  TypeError: __init__() missing 1 required positional argument: 'feature_columns'
  </code></pre>