title: Clarification of TensorFlow AttentionWrapper's Layer Size
body: <p>In <code>tensorflow.contrib.seq2seq</code>'s <code>AttentionWrapper</code>, what does "depth" refer to as stated in the <code>attention_layer_size</code> documentation? When the documentation says to "use the context as attention" if the value is <code>None</code>, what is meant by "the context"?</p>