Marshal the object and do a PUT

def save_object(self, obj, expected_value=None):
        """
        Marshal the object and do a PUT
        """
        doc = self.marshal_object(obj)
        if obj.id:
            url = "/%s/%s" % (self.db_name, obj.id)
        else:
            url = "/%s" % (self.db_name)
        resp = self._make_request("PUT", url, body=doc.toxml())
        new_obj = self.get_object_from_doc(obj.__class__, None, parse(resp))
        obj.id = new_obj.id
        for prop in obj.properties():
            try:
                propname = prop.name
            except AttributeError:
                propname = None
            if propname:
                value = getattr(new_obj, prop.name)
                if value:
                    setattr(obj, prop.name, value)
        return obj