Write loop in optimization problem constraint

Hello

I have an optimization problem that needs a loop in it's constraints.

My optimizaton problem constraint: we have some nodes that should preserve a distinct distance among each other, for this goal I've written a loop in constraints include a for loop that measure norm among every pair of nodes that should be greater than a specific 'd', but my constraint including for loop isn't met.

Have you ever used a loop (especially for loop) in constraints section of an opt. problem?