title: tensorflow.train.import_meta_graph does not work?
body: <p>I try to simply save and restore a graph, but the simplest example does not work as expected (this is done using version 0.9.0 or 0.10.0 on Linux 64 without CUDA using python 2.7 or 3.5.2)</p>
  
  <p>First I save the graph like this:</p>
  
  <pre><code>import tensorflow as tf
  v1 = tf.placeholder('float32') 
  v2 = tf.placeholder('float32')
  v3 = tf.mul(v1,v2)
  c1 = tf.constant(22.0)
  v4 = tf.add(v3,c1)
  sess = tf.Session()
  result = sess.run(v4,feed_dict={v1:12.0, v2:3.3})
  g1 = tf.train.export_meta_graph("file")
  ## alternately I also tried:
  ## g1 = tf.train.export_meta_graph("file",collection_list=["v4"])
  </code></pre>
  
  <p>This creates a file "file" that is non-empty and also sets g1 to something that looks like a proper graph definition.</p>
  
  <p>Then I try to restore this graph:</p>
  
  <pre><code>import tensorflow as tf
  g=tf.train.import_meta_graph("file")
  </code></pre>
  
  <p>This works without an error, but does not return anything at all. </p>
  
  <p>Can anyone provide the necessary code to simply just save the graph for "v4" and completely restore it so that running this in a new session will produce the same result?</p>