'Given a defaults dictionary, and any other dictionaries,
update those other dictionaries with information in defaults if
none of the other dictionaries contains that information.'

def _setdefaults(self, defaults, *kwargs):

    for k in defaults:
        if all(((kw.get(k, None) is None) for kw in kwargs)):
            for kw in kwargs:
                kw[k] = defaults[k]
