It takes experience and things can go wrong.

If you care, find someone experienced locally who can do it. It only makes sense to try it and learn it if you will need to sex some amount of ball pythons in the future, just my personal opinion. The method would be to pop it, which is no big deal for experienced people that already did it often, but on first try things can go wrong, or lets say less than perfect.

Since you are dealing with one nice-looking ball python, i would say find someone who did it 20+ times, a local breeder or a reptile vet, or leave it be.

and its true, you cannot determine the gender just by looking at it.