Is there a way to specify a constraint on the sum of two parameters when doing bayesian estimation?

For instance, I have two parameters and in `estimated_params`

block, they’re declared as

a_y1, 1.4, 1,2 , uniform_pdf, 1.5, 0.083;

a_y2, -0.597, -1,0 , uniform_pdf, -0.5, 0.083;

what is the syntax to specify the constraint that 0<a_y1+a_y2<1? Thanks!