SHERPA HEPMC output

Hi @apricePhy,

I ran the FermionProduction with a uubar final state to debug the conversion HepMC -> EDM4HEP.

HEPMC is 3.2.7, so according to page 6 of https://arxiv.org/pdf/1912.08005.pdf I would have expected the colorflow as vector when retrieving the attribute "flows", but the pointer is empty (info not present).

Here is the first event:
[SherpaOut.txt](https://github.com/key4hep/k4GeneratorsConfig/files/15021071/SherpaOut.txt)

So it seems like the colorflow is there, but coded as flow1 and flow2, which is (page 10) the pre-3.2.0 style.

Could you check whether in the sherpa 3 and/or more recent sherpa2 versions the change was made?

I guess we could do a bootstrap (check for flow1, flow2 first, if not present check for flows) to compensate, but.......

Dirk

Start with the attached SherpaOut.txt event and compare the reported HEPMC 3.2.7 behavior with the Sherpa 2 and Sherpa 3 versions mentioned in the issue. Confirm how the colorflow attributes are represented and document whether a compatibility change is needed; the issue is done when the affected versions and expected handling are established.

Written by the indexing model from the issue text.