class PermissionnMixin:

    def __init__(self):
        self.permissions = set()

    def grant_permission(self, permission):
        self.permissions.add(permission)

    def revoke_permission(self, permission):
        self.permissions.discard(permission)

    def has_permission(self, permission):
        return permission in self.permissions
    

class User(PermissionnMixin):

    def __init__(self, name, email):
        super().__init__()
        self.name = name
        self.email = email

    
def main():
    user1 = User('Alice', 'alice@example.com')
    user2 = User('Bob', 'bob@example.com')

    assert user1.email == 'alice@example.com'
    assert user1.name == 'Alice'
    assert user1.permissions == set()

    assert user2.email == 'bob@example.com'
    assert user2.name == 'Bob'
    assert user2.permissions == set()

    user1.grant_permission('read')
    user1.grant_permission('write')
    user2.grant_permission('read')
    assert user1.permissions == {'read', 'write'}
    assert user2.permissions == {'read'}

    assert user1.has_permission('read') is True
    assert user1.has_permission('write') is True
    assert user1.has_permission('execute') is False

    assert user2.has_permission('read') is True
    assert user2.has_permission('write') is False
    assert user2.has_permission('execute') is False

    user1.revoke_permission('write')
    user1.revoke_permission('execute')

    assert user1.has_permission('read') is True
    assert user1.has_permission('write') is False
    assert user1.has_permission('execute') is False

    print('Good')


if __name__ == '__main__':
    main()