def setdefault(self, key, default=None):
            if key in self:
                return self[key]
            self[key] = default
            return default
od.setdefault(k[,d]) -> od.get(k,d), also set od[k]=d if k not in od
dataset/ETHPy150Open xraypy/xraylarch/doc/sphinx/ext/backports.py/OrderedDict.setdefault