def inorder_iter(self):  
        element = self.korzen  
        stos = []

        while True: 
            if element is not None: 
                stos.append(element) 
                element = element.left_node  

            elif(stos): 
                element = stos.pop() 
                print(element.dane) 

                element = element.right_node
            else: 
                break