I sample my model with two chains and 600 draws each. Then I sample the

posterior predictive, using `pm.sample_posterior_predictive()`

(or its speedy cousin `pm.fast_sample_posterior_predictive()`

). The posterior predictive dataset has one chain and 1200 draws.

Why does sampling the posterior predictive use only one chain instead of the two in the posterior? Maybe I shouldn’t care about this: 1x1200 is maybe equivalent to 2x600. But a subsequent call to `pm.summary()`

on the posterior predictive group makes numerous warnings about the change in shape:

Should these warnings be ignored?