#### Binary Tree Node Sum

p
```"""
Sum of all nodes in a binary tree.

Python implementation:
O(n) time complexity - Recurses through :meth:`depth_first_search`
with each element.
O(n) space complexity - At any point in time maximum number of stack
frames that could be in memory is `n`
"""

from __future__ import annotations

from collections.abc import Iterator

class Node:
"""
A Node has a value variable and pointers to Nodes to its left and right.
"""

def __init__(self, value: int) -> None:
self.value = value
self.left: Node | None = None
self.right: Node | None = None

class BinaryTreeNodeSum:
r"""
The below tree looks like this
10
/  \
5   -3
/    / \
12   8  0

>>> tree = Node(10)
>>> sum(BinaryTreeNodeSum(tree))
10

>>> tree.left = Node(5)
>>> sum(BinaryTreeNodeSum(tree))
15

>>> tree.right = Node(-3)
>>> sum(BinaryTreeNodeSum(tree))
12

>>> tree.left.left = Node(12)
>>> sum(BinaryTreeNodeSum(tree))
24

>>> tree.right.left = Node(8)
>>> tree.right.right = Node(0)
>>> sum(BinaryTreeNodeSum(tree))
32
"""

def __init__(self, tree: Node) -> None:
self.tree = tree

def depth_first_search(self, node: Node | None) -> int:
if node is None:
return 0
return node.value + (
self.depth_first_search(node.left) + self.depth_first_search(node.right)
)

def __iter__(self) -> Iterator[int]:
yield self.depth_first_search(self.tree)

if __name__ == "__main__":
import doctest

doctest.testmod()
```