if the ``name`` is set, return its value.  Otherwse set ``name`` to
            ``value`` and return ``value``

def setdefault(self, name, value):
        ''' if the ``name`` is set, return its value.  Otherwse set ``name`` to
            ``value`` and return ``value``'''
        if name in self:
            return self[name]
        self[name] = value
        return self[name]