title: Why does Tensorflow Reshape tf.reshape() break the flow of gradients?
body: <p>I am creating a <code>tf.Variable()</code> and then create a simple function using that variable, then I flatten the original variable using <code>tf.reshape()</code> and then I take the <code>tf.gradients()</code> between the function and the flattened variable. Why does that return <code>[None]</code>.</p>
  <pre><code>var = tf.Variable(np.ones((5,5)), dtype = tf.float32)
  f = tf.reduce_sum(tf.reduce_sum(tf.square(var)))
  var_f = tf.reshape(var, [-1])
  print tf.gradients(f,var_f)
  </code></pre>
  <p>The above codeblock when executed returns <code>[None]</code>. Is this a bug? Please Help!</p>