exercise6 Lesson02/Exercise06/models/recipe.py int value is added an id attribute last_recipe.id + 1

[v6msee]

recipe_list = []


def get_last_id():
    if recipe_list:
        last_recipe = recipe_list[-1]
    else:
        return 1
    return last_recipe.id + 1

In the last line how id is added ?