title: Save tensorflow checkpoint to .pb protobuf file
body: <p>I have trained a <a href="https://github.com/affinelayer/pix2pix-tensorflow" rel="noreferrer">pix2pix</a> model on tensorflow and the model has been saved in the form of checkpoints with the following files:</p>
  
  <p><code>model-15000.meta</code>, <code>model-15000.index</code>, <code>model-15000.data-00000-of-00001</code>, <code>graph.pbtxt</code>, <code>checkpoint</code>.</p>
  
  <p>Now, I want to convert it to a protobuf file (.pb) for deployment purposes. I came across the <a href="https://github.com/tensorflow/tensorflow/blob/master/tensorflow/python/tools/freeze_graph.py" rel="noreferrer">freeze_graph.py</a> script to do so, but I am facing trouble with one of the arguments, it being <code>output_node_names</code>. </p>
  
  <p>I have tried out a couple of layer names, but I get the following error:</p>
  
  <blockquote>
    <p>AssertionError: generator/decoder_2/batchnorm/scale/gradients is not in graph</p>
  </blockquote>
  
  <p>Unsure how to find the output_node_names</p>