Multithreading does not work for isotope calculation

[machth]

In development branch, running IsotopeGenerator fails for unknown modifications and new nomenclature with "_" instead of " " (e.g. @Any_N-term instead of @Any N-term), but it works if you set threads = 1.
therefore, some issue occur with multithreading, probably still using the original mod df tables (from main) and not the updated ones (from development).

[jalew188]

Can you also provide the code and the logs?

[jalew188]

If the PTM is added by yourself in the GUI or in a notebook, then it is not pickled due to spawn multiprocessing. @GeorgWa we should use multi-threading instead of multiprocessing.