title: Backpropagation through time in stateful RNNs
body: <p>If I use a stateful RNN in Keras for processing a sequence of length N divided into N parts (each time step is processed individually),</p>
  
  <ol>
  <li>how is backpropagation handled? Does it only affect the last time step, or does it backpropagate through the entire sequence? </li>
  <li>If it does not propagate through the entire sequence, is there a way to do this?</li>
  </ol>