I firmly believe that temperament is inherent--my newly hatched babies run the gamut of personality from very laid-back, outgoing, and curious, to little spitfires that try to kill anything that comes near them with their teeth.
These personalities evolve over time--most of the nervous snakes, and some of the bitey ones, will calm down as they grow older. But I have never seen this happen the other way around.

If a snake is going to be a pain as an adult, it pretty much is sure to have started out that way, too.

Whether genetics play a role in this remains to be seen, but they have been PROVEN to play a role in other species, so it's a fair assumption that they DO.
Because of that, I will not breed a snake with a bad temperament--I don't keep them. I don't hold back bad-tempered hatchlings. I don't BUY bad-tempered snakes.

For me, a quality captive ball python is one that is temperamentally suited to be a captive, and a pet. That is an essential component to 'quality' for any animal intended to be a pet. I do not buy into the idea that 'these are wild animals', and that defensive bites are something you just have to put up with. Most of my snakes have never bitten in self-defense. We keep these animals as pets--we're responsible for choosing which ones to breed, and for selecting traits that will make them better PETS--in other words, we are responsible for continuing the process of DOMESTICATING them.

Accidental feeding bites are completely different. Actually startling a snake is also completely different--your pet dog or cat may bite you if you startle them badly enough. But biting when they see you coming--that's not startlement. I do not believe adult CBB ball pythons that display a willingness to bite rather than be handled are high quality.