Python3 syntax in Lowest common ancestor

Question

Classic problem of LCA in BT: Given a Binary Tree find the lowest common ancestor. I found a Python2 solution but don't know how to fix it in Python3.

# This is Python2, but having error in Python3 such that 
# parent += node if all(subs) else max(subs),
# TypeError: '>' not supported between instances of 'NoneType' and 'NoneType'`

# lca.py
class Solution:
    def lowestCommonAncestor(self, root, p, q):
        answer = []
        stack = [[root, answer]]

        while stack:
            top = stack.pop()
            (node, parent), subs = top[:2], top[2:]

            if node in (None, p, q):
                parent += node,
            elif not subs:
                stack += top, [node.right, top], [node.left, top]    
            else:
                parent += node if all(subs) else max(subs),     # this is the problem in Python3
        return answer[0]

s = Solution()
root = tree.create_tree3()
p = tree.find(root, 6)
q = tree.find(root, 1)
print(f'p = {p}, q = {q}')

lca = s.lowestCommonAncestor(root, p, q)

print(f"lca = {lca}")

# tree.py
class TreeNode:
    def __init__(self, val, left=None, right=None):
        self.val = val
        self.left = left
        self.right = right

    def __repr__(self):
        return str(self.val)

def find(root, val):
    if root is None:
        return None

    if root.val == val:
        return root

    left = find(root.left, val)
    right = find(root.right, val)

    if left is not None:
        return left
    else:
        return right

"""
                3
         5              1
     6      2         0   8
           7 4
"""
def create_tree3():
    n3 = TreeNode(3)
    n5 = TreeNode(5)
    n1 = TreeNode(1)
    n6 = TreeNode(6)
    n2 = TreeNode(2)
    n0 = TreeNode(0)
    n8 = TreeNode(8)
    n7 = TreeNode(7)
    n4 = TreeNode(4)

    n3.left, n3.right = n5, n1
    n5.left, n5.right = n6, n2
    n1.left, n1.right = n0, n8
    n2.left, n2.right = n7, n4

    return n3

I'm a newbie of Python3 and trying to fix this error in Python3, and I'm trying below, but not working.

class Solution:
    def lowestCommonAncestor(self, root, p, q):
        answer = []
        stack = [[root, answer]]

        while stack:
            top = stack.pop()
            (node, parent), subs = top[:2], top[2:]

            if node in (None, p, q):
                parent += node,
            elif not subs:
                stack += top, [node.right, top], [node.left, top]   
            else:
                if subs[0] and subs[1]:
                    parent += node
                else:               # not sure how to fix the below part which is not working either
                    if subs[0] and not subs[1]:
                        parent += subs[0]
                    elif not subs[0] and subs[1]:
                        parent += subs[1]
                    elif not subs[0] and not subs[1]:
                        parent += None

        return answer[0]