def __missing__(self, key):
        if self.default_factory is None:
            raise KeyError(key)
        else:
            ret = self[key] = self.default_factory(name=key)
            return ret
def foam_arch(self):
        if not self._foam_arch:
            self._foam_arch = OpenfoamOrgArch(self.spec, **self.config)
        return self._foam_arch