I am trying to type check a persistent (immutable) data structure. However I am stumbling on restrictions on using covariant types as arguments. Is there a standard work around for this?

Simplified Example:

class Node(Generic[T_co]):
    def __init__(self, val: T_co, succ: Optional[Node[T_co]]) -> None:
        self.val: Final[T_co] = val
        self.succ: Final[Optional[Node[T_co]]] = succ

class List(Sequence[T_co]):
    def __init__(self, *, _head: Optional[Node[T_co]] = None) -> None:
        self.head: Final[Optional[Node[T_co]]] = _head

    # The problem method
    def push_front(self, val: T_co) -> List[T_co]:
        new_node = Node(val, self.head)
        return List(_head=new_node)

    def __iter__(self) -> Iterator[T_co]:
        ptr = self.head
        while ptr is not None:
            yield ptr.val
            ptr = ptr.succ