title: gremlin-python - unable to add edge property
body: <p>I'm having great trouble adding properties to an edge using the <code>gremlin_python</code> wrapper.</p>
  
  <p>I'm able to create the edge, as so:</p>
  
  <pre><code>eid1='123'
  eid2='456'
  edge = g.V().has('eid', eid1).addE('transaction').to(g.V().has('entity_id',eid2)).next()
  </code></pre>
  
  <p>But, adding properties to the edge doesn't work. As in: the code runs without error, but no changes occur on the edge itself, so when after I call <code>g.E(edge).valueMap.toList()</code>, it returns an empty list.</p>
  
  <pre><code>g.E(edge).property('foo','bar').iterate()    &lt;-- I've also tried this without iterate.
  </code></pre>
  
  <p>It also doesn't work if I create the node and add a property on the same line of code.</p>
  
  <p>The same code - but executed in the gremlin console - runs as expected. i.e., after creating the edge and assigning the property:</p>
  
  <pre><code>gremlin&gt; g.E(edge).valueMap().toList()
  ==&gt;{foo=bar}
  </code></pre>
  
  <p>Any help here would be greatly appreciated.</p>
  
  <hr>
  
  <p><strong>Update</strong></p>
  
  <p>I was unable to get this to work using the python wrapper on the graph traversal object, instead I ran the code through the client, which works as expected. But this is a workaround, and not a solution.</p>
  
  <pre><code>gremlin_client = client.Client('ws://localhost:8182/gremlin', 'g')
  
  query = "g.V().has('eid', '123').addE('transaction').to(g.V().has('eid','456')).property('foo','bar').next()"
  gremlin_client.submit(query).all().result()
  </code></pre>