(self, node)
return self.level - node.level
If node is ancestor of self
                Get the difference in level
                If not, None
If node is ancestor of self
                Get the difference in level
                If not, None
If node is ancestor of self Get the difference in level If not None
def is_ancestor(self, node):
        """
                If node is ancestor of self
                Get the difference in level
                If not, None
        """
        if self.level <= node.level or self.key[:len(node.key)] != node.key:
            return None
        return self.level - node.level
def is_ancestor ( self , node ) : if self . level <= node . level or self . key [ : len ( node . key ) ] != node . key : return None return self . level - node . level