Method __init__

example_code/item_054.py:96–104

(
        self,
        value,
        left=None,
        right=None,
        parent=None,
    )

print("Example 4")
class BinaryTreeWithParent(BinaryTree):
    def __init__(
        self,
        value,
        left=None,
        right=None,
        parent=None,
    ):
        super().__init__(value, left=left, right=right)
        self.parent = parent

    def _traverse(self, key, value):
        if (