code: public boolean setFanSpeed(int speed) throws CommandExecutionException {
          if (speed < 0 || speed > 100) throw new CommandExecutionException(CommandExecutionException.Error.INVALID_PARAMETERS);
          JSONArray params = new JSONArray();
          params.put(speed);
          return sendOk("set_custom_mode", params);
      }
docs: Set the vacuums fan speed setting.
  @param speed The new speed to set.
  @return True if the command has been received correctly.
  @throws CommandExecutionException When there has been a error during the communication or the response was invalid.