def level(self, curr_node=None, ilosc=0):

        if curr_node is None:
            curr_node = self.korzen

        if curr_node:
            if curr_node.left_node is not None:
                ilosc += self.level(curr_node.left_node)

            if curr_node.right_node is not None:
                ilosc += self.level(curr_node.right_node)

            if curr_node.right_node is not None and curr_node.left_node is not None:
                ilosc += 1

        return ilosc