How does the MPS writer of Gurobi work?

```
using JuMP, Gurobi
model = Model(Gurobi.Optimizer)
@variables(model, begin
0 <= x <= 5
0 <= y <= 10, Int
z, Bin
end)
@objective(model, Max, x + 2y + 5z)
@constraint(model, x + y + z <= 10)
@constraint(model, x + 2y + z <= 15)
Gurobi.write_model(model.moi_backend.optimizer.model.inner, "test.mps")
```

gives me an empty file:

```
NAME
ROWS
N OBJ
COLUMNS
RHS
BOUNDS
ENDATA
```

`JuMP.write_to_file(model, "test_JuMP.mps")`

would work.

The reason seems to be that the `inner`

model is empty until `optimize!`

is called.

How do I transfer the model without a call of `optimize!`

?