title: TensorFlow: Add dimension (column) with constant value
body: <p>I have a Tensor of shape <code>(-1,)</code> which represents a list of indices. I want to create a Tensor of shape <code>(-1,2)</code>. The first column should be the same as the list of indices, while the second column should be filled with a constant.</p>
  <p>Eg (let's say the constant is 6):</p>
  <pre><code>indices = [4, 35, 230, 235]
  my_goal = [[4, 6], [35, 6], [230, 6], [235, 6]]
  </code></pre>
  <p>What is the best way to do this? I was hoping a broadcasting-<code>tf.concat</code> would work, but <code>tf.concat</code> doesn't seem to support broadcasting.</p>