Turn off receiver via HTTP get command.

def power_off(self):
        """Turn off receiver via HTTP get command."""
        try:
            if self.send_get_command(self._urls.command_power_standby):
                self._power = POWER_STANDBY
                self._state = STATE_OFF
                return True
            else:
                return False
        except requests.exceptions.RequestException:
            _LOGGER.error("Connection error: power off command not sent.")
            return False