Think about the "ops" handling

https://github.com/FireDynamics/propti/blob/c938244800ecb7b3381e517792e3a5d778bd6184/propti_prepare.py#L44

Is it a good idea to have the `ops` decoupled from everything? Wouldn't it be better to have it connected to something, like maybe the simulation setup or the optimiser properties or something? Otherwise it is lying around somewhat on its own and is likely confusing to others.