human
Complete the below
def do_one(*brules):

    ''''Execute one of the branching rules'
    '''

=====
Can you provide a the Python program you requested?
assistant
#Here is the Python program you requested.
    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