code: public static Progression subToEnd(Progression model) {
  		if (model != null) {
  			return model.subTask(model.getMaximum() - model.getValue());
  		}
  		return null;
  	}
docs: Create and replies a task progression model that is for
  a subtask of the task associated to the given progression model.
  
  <p>The subtask progression model is not initialized.
  When the subtask progression model reaches its end,
  the value of the task progression is equal to the maximum.
  
  @param model is the model to derivate
  @return the subtask progression model; or <code>null</code>.