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 __init__(self, config_d, path=None, resolver=None):
        super().__init__(path=path, resolver=resolver)
        self._collection = {}
        for key, value in config_d.items():
            self._collection[key] = self._from_python(key, value)