Given a log_prob_parts function, this function will return a new one that
includes all-reduce sums over terms according to the is_sharded property. It
will also add all-reduce sums for the gradient of sharded terms w.r.t.
a callable that takes in a structured value and returns a
structure of log densities for each of the terms, that when summed returns
a locally correct log-density.
a structure of boolean values that matches the input and output
of log_prob_parts_fn. If a value in log_prob_parts_fn has a
corresponding is_sharded value set to True, the returned function will
add an all-reduce sum for its term in the log prob calculation. If it is
False, the returned function will have an all-reduce sum over the
gradient of sharded terms w.r.t. to the unsharded value.
a str used for the axis name in the JAX backend. Unused in the
A new log prob parts function that can be run inside of strategy.