title: Filter a tensor on the basis of a python list in TensorFlow
body: <p>I have a tensor <code>a</code> of type <code>tf.int64</code>. I want to filter out this tensor on the basis of a given python list.<br>
  For example -         </p>
  
  <pre class="lang-py prettyprint-override"><code>l = [1,2,3]
  a = tf.constant([1,2,3,4], dtype=tf.int64) 
  </code></pre>
  
  <p>Need a tensor with values <code>1,2,3</code> except <code>4</code>. That is filtering out <code>a</code> on the basis of <code>l</code>. How can I do this in TensorFlow?</p>