python – I have a script about class and inheritance get the info about student has already graduated or not

I have a script like below
I want to optimzize my code

class Person:
def __init__(self, fname, lname):
    self.fname = fname
    self.lname = lname

class Student(Person):
def __init__(self, fname, lname, isgraduated):
    super().__init__(fname, lname)
    self.isgraduated = isgraduated

def check_graduated(self):
    yes = 'graduated'
    no = "haven't graduated yet"

    return yes if self.isgraduated else no

def introduce_self(self):
    statement = ''
    if self.isgraduated:
        statement += 'congratulation!'
        statement += "I'm sorry"
    return f'Hi {self.lname} {self.fname}, {statement} you {self.check_graduated()}'

Any neat Pythonic way make my code cleaner? Thank for reading