Set receiver volume via HTTP get command.

        Volume is send in a format like -50.0.
        Minimum is -80.0, maximum at 18.0

def set_volume(self, volume):
        """
        Set receiver volume via HTTP get command.

        Volume is send in a format like -50.0.
        Minimum is -80.0, maximum at 18.0
        """
        if volume < -80 or volume > 18:
            raise ValueError("Invalid volume")

        try:
            return bool(self.send_get_command(
                self._urls.command_set_volume % volume))
        except requests.exceptions.RequestException:
            _LOGGER.error("Connection error: set volume command not sent.")
            return False