Very strange AttributeError

I have a class Menu with append_option Method:

class Menu:

    def __init__(self):
        self._option_surfaces = []
        self._callbacks = []
        self._current_option_index = 0

    def append_option(self, option, callback, font):
        self._option_surfaces.append(font.render(option, True, (255, 255, 255)))
        self._callbacks.append(callback)

I create an instance of this class.

menu = Menu()

font = pygame.font.Font('Rostov.ttf', 60)

menu.append_option('Play', lambda: print('Oh hell nah man'), font)

But the python has a different opinion

    menu.append_option('Play', lambda: print('Oh hell nah man'), font)
    ^^^^^^^^^^^^^^^^^^
AttributeError: 'Menu' object has no attribute 'append_option'

I tried to rename method, replace lines but nothing changed.

How can I solve this problem?

I ran your code as follows, and I didn't get any errors:

import pygame
pygame.init()

class Menu:

    def __init__(self):
        self._option_surfaces = []
        self._callbacks = []
        self._current_option_index = 0

    def append_option(self, option, callback, font):
        self._option_surfaces.append(font.render(option, True, (255, 255, 255)))
        self._callbacks.append(callback)

menu = Menu()

menu.append_option('Play', lambda: print('Oh, hell nah man'), pygame.font.Font('Rostov.ttf', 60))

Check your IDE, or something else is wrong.