my one true distribution of a and then you essentially average out this conditional distribution that would be the marginal distribution of p and ideally I warn my Q to be close to the ground truth conditional distribution P of P given a and that means if I sample a lot of a and then I map it through my conditional distribution the outcome of that should map back to the original ground true of distribution and similarly I can do that for a so I sample from B and then I would from from this B samples I would calculate my