def save(self, filename=None):
        filename = Path(filename) if filename is not None else self.filename
        with filename.open("w") as f:
            f.write(self.yaml)
def foam_arch(self):
        if not self._foam_arch:
            self._foam_arch = OpenfoamOrgArch(self.spec, **self.config)
        return self._foam_arch