from dataclasses import dataclass
from typing import List, Optional, TypeVar


@dataclass
class UserBase:
    id: int
    first_name: str
    last_name: str


@dataclass
class Employee(UserBase):
    department: str


@dataclass
class Partner(UserBase):
    company: str


UserContainerType = TypeVar("UserContainerType", bound=UserBase)


class UserContainer(List[UserContainerType]):
    def get_user_by_id(self, id: int) -> Optional[UserContainerType]:
        for user in self:
            if user.id == id:
                return user
        return None


class EmployeeContainer(UserContainer[Employee]):
    def get_by_department(self, department: str) -> List[Employee]:
        return [user for user in self if user.department == department]


class PartnerContainer(UserContainer[Partner]):
    def get_by_company(self, company: str) -> List[Partner]:
        return [user for user in self if user.company == company]