title: What is the architecture behind the Keras LSTM cell?
body: <p>I am doing a project about sequence model.  When I read this <a href="https://arxiv.org/pdf/1503.04069.pdf?utm_content=buffereddc5&amp;utm_medium=social&amp;utm_source=plus.google.com&amp;utm_campaign=buffer" rel="nofollow noreferrer">paper</a>, I found there are lots of variants of LSTM.  what confuses me is that I am not clear the architecture behind the Keras when using <a href="https://keras.io/layers/recurrent/" rel="nofollow noreferrer">LSTM cell</a>. Can someone tell me which LSTM architecture used in Keras? Is <a href="https://i.stack.imgur.com/RHNrZ.jpg" rel="nofollow noreferrer">picture-1</a>？ or <a href="https://i.stack.imgur.com/voZql.jpg" rel="nofollow noreferrer">picture-2</a>? or others?</p>
  
  <p><a href="https://i.stack.imgur.com/RHNrZ.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/RHNrZ.jpg" alt="picture-1"></a>
  <a href="https://i.stack.imgur.com/voZql.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/voZql.jpg" alt="picture-2"></a></p>
  
  <p>The version of Keras I used is 2.1.5.</p>