prox operator for functions composed with linear operator g(x) = f(Ax)

[ryanvolz]

If A is orthogonal, this is trivial. Is it worth implementing other special cases, or particular functions that use this? See the following for possible examples:
Combettes and Pesquet (2011), "Proximal Splitting Methods in Signal Processing"
Pustelnik et al. (2011), "Parallel Proximal Algorithm for Image Restoration Using Hybrid Regularization"
Pustelnik et al. (2012), "Relaxing Tight Frame Condition in Parallel Proximal Methods for Signal Restoration"
Becker and Fadili (2012), "A quasi-Newton proximal splitting method"