Send a message to the backend.

        :param reason: Reason of the message.
        :param message: Message content.

def send(self, event, message):
        """Send a message to the backend.

        :param reason: Reason of the message.
        :param message: Message content.
        """
        self.connection.send({
            'reason': ['request', 'send'],
            'content': {
                'reason': event,
                'request_id': self.request_counter,
                'content': message,
            },
        })
        self.request_counter = self.request_counter + 1