I really like that minipyro is in here for those interested in the internals of pyro. Super awesome!

Some of the wording in the module, particularly regarding PYRO_STACK, is confusing to me, though.

For example:

If we run:

trace(replay(model, guide_trace)).get_trace(...)

We end up (somewhere during the execution of the above line) with a PYRO_STACK with the first item referencing trace, and the second item referencing replay. But when we hit apply_stack, because of the reverse order in which the handlers are applied, replay is applied first. So, the comments should read, # Handlers *later* in the PYRO_STACK are applied first., correct?

Similarly, in

Shouldn't

When a Messenger sets the "stop" field of a message,
it prevents any Messengers above it on the stack from being applied.

really be:

When a Messenger sets the "stop" field of a message,
it prevents any Messengers below it on the stack from being applied.

And

A Messenger that sets msg["stop"] == True also prevents application
of postprocess_message by Messengers above it on the stack
via the pointer variable from the process_message loop

should really be:

A Messenger that sets msg["stop"] == True also prevents application
of postprocess_message by Messengers below it on the stack
via the pointer variable from the process_message loop

I could be convinced to interpret all this otherwise, but I guess this was my default interpretation. Am I way off-base?