Implementing conditional sampling over sum of variables

Misc.
1

I am a beginner with Pyro and I want to know how to implement conditional samples. Say I want to build a model for two dice throws. Say that we saw the first die, and it’s a 4. Now, I want to get a distribution of the sum of the numbers on the two dice.

Using pyro.model, I can independently sample values from two dist.Categorical([0.16, 0.16, 0.16, 0.16, 0.16, 0.16]) something as follows(?):

def model():
    dice1 = pyro.sample("dice1", dist.Categorical([0.16, 0.16, 0.16, 0.16, 0.16, 0.16]))
    dice2 = pyro.sample("dice2", dist.Categorical([0.16, 0.16, 0.16, 0.16, 0.16, 0.16]))
    return dice1 + dice2

In the above, how do I add the condition that dice1 == 4 || dice2 == 4.