I made a helper function for constraints

```
"""
If x is Bin & y is Int, it simply means x = y % 2.
"""
function addParityConstraint(model::JuMP.Model, x, y)
@variable(model, odd_dummy, Int)
@constraint(model, x + y == 2 * odd_dummy)
end
```

But keeps getting

```
WARNING: A variable named odd_dummy is already attached to this model.
If creating variables programmatically, consider using the anonymous variable syntax x = @variable(m, [1:N], ...).
```

How to avoid the warnings? I cannot get anonymous variable with types working, e.g. `@variable(model, Int)`