Since you know that youâ€™re using Gurobi, you should use JuMP in direct-mode. The new syntax would be:

```
model = JuMP.direct_model(Gurobi.Optimizer())
@variable(model, x >= 0)
@constraint(model, c, 2x >= 1)
grb = JuMP.backend(model)
row = grb[JuMP.index(c)]
Gurobi.set_intattrelement!(grb.inner, "Lazy", row, 3)
```

If you use this a lot, itâ€™d be a nice contribution to add this as a MOI attribute, similar to the in-progress IIS: https://github.com/JuliaOpt/Gurobi.jl/pull/208

Then the syntax would be

```
model = Modle(with_optimizer(Gurobi.Optimizer))
@variable(model, x >= 0)
@constraint(model, c, 2x >= 1)
MOI.set(model, Gurobi.Lazy(), c, 3)
```

or even

```
model = Modle(with_optimizer(Gurobi.Optimizer))
@variable(model, x >= 0)
@constraint(model, c, 2x >= 1)
MOI.set(model, Gurobi.ConstraintAttribute("lazy"), c, 3)
```

Let me know, and we can point you in the right direction.