human
I wrote the below code

    def multiplex_brl(expr):
        seen = set([])
        for brl in brules:
            for nexpr in brl(expr):
                if (nexpr not in seen):
                    seen.add(nexpr)
                    (yield nexpr)
    return multiplex_brl

What's a good function header?
assistant
#Here's a good function header.

def multiplex(*brules):