Superbalanced

def is_superbalanced(root_node):
    
    depths = set()
    node_stack = [(root_node, 0)]
    
    while node_stack:
        node, depth = node_stack.pop()
        print("node.value:", node.value)
        print("depth:", depth)
        
        if not node.left and not node.right:
            depths.add(depth)
            print("Set:", depths)
            
            size = len(depths)
            if size>2 or (size == 2 and abs(depths.pop()-depths.pop())>1):
                return False
            
        if node.left:
            node_stack.append((node.left, depth+1))

        if node.right:
            node_stack.append((node.right, depth+1))

    return True
    
class BinaryTree(object):

    def __init__(self, value):
        self.value = value
        self.left  = None
        self.right = None

    def insert_left(self, node):
        self.left = node
        return self.left.left

    def insert_right(self, node):
        self.right = node
        return self.right.right

node_7 = BinaryTree(7)
node_8 = BinaryTree(8)
#node_8.insert_left(node_7)
    
node_1 = BinaryTree(1)
node_1.insert_left(node_8)
node_5 = BinaryTree(5)
node_6 = BinaryTree(6)

node_2 = BinaryTree(2)
node_2.insert_left(node_1)

node_4 = BinaryTree(4)
node_4.insert_right(node_5)

node_3 = BinaryTree(3)
node_3.insert_left(node_2)
node_3.insert_right(node_4)

root = node_3
print(is_superbalanced(root))