code: def increment(self, key, amount=1):
          
          payload = {
              key: {
                  '__op': 'Increment',
                  'amount': amount
                  }
              }
          self.__class__.PUT(self._absolute_url, **payload)
          self.__dict__[key] += amount
docs: Increment one value in the object. Note that this happens immediately:
          it does not wait for save() to be called