title: Modify or change relationship properties in py2neo
body: <p>Is there a way to change a relationship property once it has been set using py2neo or cypher? I'm creating an inventory tracker and once an item is "CHECKED_OUT" a property called "status" in the relationship is set to "True". Ideally, once the item is returned or checked in, I'd like to change the "status" property to "False". This way I can keep track of the item and prevent it from being checked out twice.</p>
  
  <p>Here is my code for creating the relationship for a checkout transaction:</p>
  
  <pre><code>    def check_out(self, barcode):
          emp = self
          item = barcode
          id = str(uuid.uuid4())
          timestamp = int(datetime.now().strftime("%s"))
          date = datetime.now().strftime("%F")
          status=True
          rel = Relationship(emp, "CHECKED_OUT", item, id=id, timestamp=timestamp, date=date, status=status)
          if not(graph.create_unique(rel)):
              return True
          else:
              return False
  </code></pre>
  
  <p>I've read through the py2neo API and I can't seem to find the answer. If modifying the relationship is the wrong approach, can you offer a better one? </p>