docs: public int getSoundVolume() throws CommandExecutionException {
          JSONArray res = sendToArray("get_sound_volume");
          if (res == null) throw new CommandExecutionException(CommandExecutionException.Error.INVALID_RESPONSE);
          int vol = res.optInt(0, -1);
          if (vol < 0) throw new CommandExecutionException(CommandExecutionException.Error.INVALID_RESPONSE);
          return vol;
      }