Send a request to the device to play a sound.

        It's possible to pass a custom message by changing the `subject`.

def play_sound(self, subject='Find My iPhone Alert'):
        """ Send a request to the device to play a sound.

        It's possible to pass a custom message by changing the `subject`.
        """
        data = json.dumps({
            'device': self.content['id'],
            'subject': subject,
            'clientContext': {
                'fmly': True
            }
        })
        self.session.post(
            self.sound_url,
            params=self.params,
            data=data
        )