freeing fixed variables

Is it possible to “free” a variable in an existing model, such that its value is removed, and the corresponding model, when solved, treats that variable as a free variable?

In an existing model m, I tried m["C_L"].key.descr.pop("value"), but it doesn’t actually remove the value from the descr. I also don’t know if other changes would be needed to Model to implement this robustly.

… or maybe there’s a much smarter way to accomplish converting fixed variables in an existing model to free variables?

[bqpd]

We test this in t_model/test_cost_freeing

[bqpd]

It’s also in the docs at https://gpkit.readthedocs.io/en/latest/advancedcommands.html#freeing-fixed-variables