code: def verify(self, secret_key):
          
          verification_input = NotificationMessage.SERVICE_NAME
          verification_input += NotificationMessage.OPERATION_NAME
          verification_input += self.timestamp
          h = hmac.new(key=secret_key, digestmod=sha)
          h.update(verification_input)
          signature_calc = base64.b64encode(h.digest())
          return self.signature == signature_calc
docs: Verifies the authenticity of a notification message.
  
          TODO: This is doing a form of authentication and
                this functionality should really be merged
                with the pluggable authentication mechanism
                at some point.