Write a function to see if a binary tree is "superbalanced" (a new tree property we just made up).
A tree is "superbalanced" if the difference between the depths of any two leaf nodes is no greater than one.
Here's a sample binary tree node class:
class BinaryTreeNode(object):
def __init__(self, value):
self.value = value
self.left = None
self.right = None
def insert_left(self, value):
self.left = BinaryTreeNode(value)
return self.left
def insert_right(self, value):
self.right = BinaryTreeNode(value)
return self.right