python二叉树递归求和

class BiTNode:
    def  __init__(self, data, left, right):
        self.data = data
        self.left = left
        self.right = right
t = BiTNode(10, BiTNode(2,None,None), BiTNode(3,None,None))
def sum_tree(t:BiTNode):
    total=0
    if t != None:
        total += t.data
        total += sum_tree(t.left)
        total += sum_tree(t.right)
    
    return total
sum_tree(t)

15