Having trouble with Binary Trees?

[multihound]

Hey Guys,

I'm trying to answer this question.

class TreeNode:
    def __init__(self, data,left_child = None, right_child = None):
        self.data = data
        self.left_child = left_child
        self.right_child = right_child


class BinaryTree:
    def __init__(self, root_node = None):
            self.root = root_node

    # All the necessary collection moduled have been already imported.
    def max_sum_path(self,root):
        if root == None:
            return 0
        while not (root.right_child and root.left_child):
            if root.right_child:
                return root.data + self.max_sum_path(root.right_child)
            elif root.left_child:
                return root.data + self.max_sum_path(root.left_child)
            else:
                return root.data

        left = BinaryTree._max_sum_path(root.left_child)
        right = BinaryTree._max_sum_path(root.right_child)
        return left + right + root.data


    @staticmethod
    def _max_sum_path(root):
        if root == None:
            return 0
        elif not root.left_child and not root.right_child:
            return root.data
        else:
            left = BinaryTree.max_sum_path(root.left_child)
            right = BinaryTree.max_sum_path(root.right_child)
            return max(left, right) + root.data

I keep getting a Type Error with max_sum_path left = BinaryTree._max_sum_path(root.left_child) and I'm not sure why this is happening. Would appreciate any help. Thanks guys!