def cleanup(channel_or_chan_list):
    pass


def gpio_function(pin):
    pass

def cleanup(channel_or_chan_list=None):
    pass


def gpio_function(pin):
    pass

Make channel an optional parameter
Make channel an optional parameter

RPi.GPIO supports calling cleanup() without parameters to cleanup
all gpios used in the session. By adding "=None" warnings about
missing parameters are ignored.
