human
Complete this python program:
def do_one(*brules):
assistant
#Here is the Python code you requested.

    """Execute one of the branching rules
    """
    def do_one_brl(expr):
        yielded = False
        for brl in brules:
            for nexpr in brl(expr):
                yielded = True
                (yield nexpr)
            if yielded:
                return
    return do_one_brl