def get_discount_node_id(self, node_id, settings):
        discount = math.exp(-settings.discount_param * self.max_split_costs[node_id])
        return discount
compute discount for a node (function of discount_param, time of split and time of split of parent)
dataset/ETHPy150Open balajiln/mondrianforest/src/mondrianforest.py/MondrianTree.get_discount_node_id