from dataclasses import dataclass
from enum import Enum, auto
from typing import Iterator, Optional


@dataclass
class Node[T]:
    value: T
    left: Optional['Node[T]']
    right: Optional['Node[T]']


type BinaryTree[T] = Optional[Node[T]]

class TraversalType(Enum):
    INORDER, POSTORDER, PREORDER = auto(), auto(), auto()

def traverse[T](tree: BinaryTree[T], order: TraversalType = TraversalType.INORDER) -> Iterator[T]:
    pass