node.py

class Node:
    def __init__(self, val=None):
        self.val = val
        self.left = None
        self.right = None


def get_root():
    values = iter([1, 6, 4, 7, None, None, 9, 8, None, None,
              10, None, None, 5, None, None, 2, 3, None, None, 11, None, None])

    def tree_recur(itr):
        val = next(itr)
        if val is not None:
            node = Node(val)
            node.left = tree_recur(itr)
            node.right = tree_recur(itr)
            return node

    return tree_recur(values)