At last it returns the group result G .
the subgradient of δ(f, e , e * , W t ) in line 4 is defined via the following equation: The main technique is the proximity operator for group optimization in line 5, which tries to minimize the function Q(•; a, t, λ 1 , λ 2 ) with a = 2 × W t + ∇ W δ(f, e , e * , W t )/t : In the next Section, we will present the details of this proximity for group optimization.