--pm-cmd / --dnf-cmd - ? mock

Hi guys. What options such as '--dnf-cmd' do, can you tell? Man page is pretty confusing - well to me it is - in that respect. I thought that was for 'args', parameters in other words which are available to the 'dnf' command itself but that does _not_ seem to be the case. At the same time - I hit something which might be common I'd imagine: ...   - cannot install the best update candidate for package mpfr-3.1.6-1.el8.x86_64   - cannot install both mpfr-4.1.0-8.el8.x86_64 and mpfr-3.1.6-1.el8.x86_64   - cannot install both mpfr-3.1.6-1.el8.x86_64 and mpfr-4.1.0-8.el8.x86_64 (try to add '--skip-broken' to skip uninstallable packages or '--nobest' to use not only best candidate packages) ... If '--dnf-cmd' is not for those things then how to rectify such a problem? many thanks, L.