class Student:
    def __init__(self, name: str, age: int, average_grade: int) -> None:
        self.name: str = name
        self.age: int = age
        self.average_grade: int = average_grade

    def display_info(self, output: bool = False) -> str | None:
        info: str = "Студент: {}, Возраст: {}, Средний балл: {}".format(
            self.name, self.age, self.average_grade
        )
        if output:
            return info
        print(info)

    def update_grade(self, new_grade: int) -> None:
        if 0 <= new_grade <= 100 and isinstance(new_grade, int):
            self.average_grade = new_grade
        else:
            raise ValueError("Ошика переданного аргумента")


alex_student: Student = Student(name="Alex", age=15, average_grade=60)
maria = Student(name="Мария", age=19, average_grade=70)

print(alex_student.display_info(output=True))
print(maria.display_info(output=True))

alex_student.update_grade(new_grade=39)
alex_student.display_info()
alex_student.update_grade(new_grade=-15)