I take it you're talking about breeding, say, a CITES Annex 1 species of python to a CITES annex 2 species of python?
According to
this consultation if an animal has an ancestor within four generations of any CITES annex, the animal will be considered to fall within that annex - and if you breed an animal in Annex I to an animal in Annex 2, its offspring will be considered Annex I animals.