Constrain outputs in a regression problem

Hi, everyone.

I am attempting to constrain some outputs of my regression
network, say x, y, z = model(data), where x, y, z are scalars. The
constrain that I want to impose is that when predicting all three
dependent variables, the condition “x + y <=1.0” must be
honored. Given this description, can I implement this in a forward
function?

Thank you!