Samuel Leweke

Where does the name `Tractor` come from? Maybe a more neutral name that can be understood by non-insiders would be fitting? Suggestion: `CompartmentTransportModel`

@hannahlanzrath has put some test cases on sciebo(?). If those work correctly, we can rebase and merge. However, adding some unit tests before merging would be great.

Tests pass, Jacobian appears to be correct. Please perform some tests to see if the model works or what should be changed.

> What if kI,i,j=0? Wouldn't it make sense to say that compoent j then also doesn't inhibit reaction i? Changed it to use `

I cannot reproduce the problem. The simple Michaelis-Menten test case appears to work for me. 

At $t = 0$, there is no flow. That is, the concentration of the inlet is constant 1, the concentration at the outlet is 0. For $t > 0$, we...

> The latest versions support implicit-explicit (IMEX) multirate methods. Only the ARKODE module, which handles only ODEs and (AFAIK) does not support sensitivities.

This would fix #99.

You propose to change `CSTRModel::notifyDiscontinuousSectionTransition()` to ```cpp void CSTRModel::notifyDiscontinuousSectionTransition(double t, unsigned int secIdx, const ConstSimulationState& simState, const AdJacobianParams& adJac) { if (_flowRateFilter.size() > 1) { _curFlowRateFilter = getSectionDependentScalar(_flowRateFilter, secIdx); }...

> is this done somewhere in CADET for other section dependent parameters? I couldn't find anything. I don't know either. Would need to scan through the code as well.