Definition zero_or_one_outputs_per_step_trace {A B C} tr :=
    forall x, In x tr -> @zero_or_one_outputs_per_step A B C x.

Theorem pbj_0_or_1 : forall net tr, step_async_star (params:=PB_multi_params) step_async_init net tr -> zero_or_one_outputs_per_step_trace tr.