title: py2neo: create relation with properties using batch
body: <p>I would like to create relationships with properties using batch insertion, so I tried the following example from the py2neo <a href="http://book.py2neo.org/en/latest/batches/#py2neo.neo4j.WriteBatch.create" rel="nofollow">documenation</a>:</p>
  
  <pre><code>batch = neo4j.WriteBatch(graph_db)
  batch.create(node(name="Alice"))
  batch.create(node(name="Bob"))
  #batch.create(rel(0, "KNOWS", 1, since=2006, reason="unknown")) # This would work
  property_dictionary = {"since": 2006, "reason": "unknown"}
  batch.create(rel(0, "KNOWS", 1, property_dictionary)) # Does NOT work
  batch.submit()
  </code></pre>
  
  <p>Why isn't it possible to specify a dictionary to assign the properties to the relationship?
  How can I batch-create a relationship with properties where the properties are stored in <code>SOME_PROPERTIES_VARIABLE</code>, e.g. something like that:</p>
  
  <pre><code>batch.create(rel(0, "KNOWS", 1, SOME_PROPERTIES_VARIABLE))
  </code></pre>
  
  <p>How would <code>SOME_PROPERTIES_VARIABLE</code> have to look like?</p>
  
  <p>For the batch function <code>get_or_create_indexed_relationship</code> I could simply use a dictionary for the properties, e.g.:</p>
  
  <pre><code>batch.get_or_create_indexed_relationship(my_rel_index, my_rel_key, my_rel_value, 0, "KNOWS", 1, properties=property_dictionary)
  </code></pre>
  
  <p>This is exactly what I am looking for, except that I don't want to index the relationship.</p>
  
  <p>I'm using Neo4j 1.9.2 and py2neo 1.5.1  - Thank you!</p>
  
  <p>Additional question: Is a batch after a <code>batch.submit()</code> empty or do I additionally have to execute <code>batch.clear()</code> ?</p>