title: _convertToOneOfMany in PyBrain
body: <p>I follow the PyBrain tutorial <a href="http://pybrain.org/docs/tutorial/fnn.html" rel="noreferrer">Classification with Feed-Forward Neural Networks</a> and want to build my own classifier. </p>
  
  <p>I do not understand how <code>_convertToOneOfMany</code> modifies outputs.</p>
  
  <p>Why would initial operation <code>alldata.addSample(input, [klass])</code> create more than one output neuron per class?</p>