 $$\varphi^0(\beta; f) =     \begin{cases}     \max\left\{     \max_{i\not\in T} (\frac{0}{w_i^0}+\frac{0}{{\|w_T\|}_0^0})~,~     \frac{0}{{\|w_T\|}_0^0}      \right\}      &\text {if } {|T|}=0     \\     \max\left\{     \max_{i\not\in T} (\frac{0}{w_i^0}+\frac{0}{{\|w_T\|}_0^0})~,~     \