from typing import Optional class User: def __init__( self, first_name: Optional[str] = None, last_name: Optional[str] = None, username: Optional[str] = None, ): if not first_name and not last_name and not username: raise ValueError('Необходимо указать параметры пользователя') self.first_name = first_name self.last_name = last_name self.username = username @classmethod def with_name( cls, first_name: str, last_name: str ): return cls(first_name=first_name, last_name=last_name) @classmethod def with_username( cls, username: str ): return cls(username=username) @staticmethod def is_username_allowed(username: str): return username.isalnum() and len(username) >= 5 print(stas.full_name) Убедитесь, что метод is_username_allowed возвращает False, если в него передать admin в качестве аргумента.