How to use the fvcore.common.config.CfgNode.load_yaml_with_base function in fvcore

def merge_from_file(self, cfg_filename: str, allow_unsafe: bool = True) -> None:
        loaded_cfg = _CfgNode.load_yaml_with_base(cfg_filename, allow_unsafe=allow_unsafe)
        loaded_cfg = type(self)(loaded_cfg)

        # defaults.py needs to import CfgNode
        from .defaults import _C

        latest_ver = _C.VERSION
        assert (
            latest_ver == self.VERSION
        ), "CfgNode.merge_from_file is only allowed on a config of latest version!"

        logger = logging.getLogger(__name__)

        loaded_ver = loaded_cfg.get("VERSION", None)
        if loaded_ver is None:
            from .compat import guess_version

merge_a_into_b(v, b[k])
                else:
                    b[k] = v

        if BASE_KEY in cfg:
            base_cfg_file = cfg[BASE_KEY]
            if base_cfg_file.startswith("~"):
                base_cfg_file = os.path.expanduser(base_cfg_file)
            if not any(
                map(base_cfg_file.startswith, ["/", "https://", "http://"])
            ):
                # the path to base cfg is relative to the config file itself.
                base_cfg_file = os.path.join(
                    os.path.dirname(filename), base_cfg_file
                )
            base_cfg = CfgNode.load_yaml_with_base(
                base_cfg_file, allow_unsafe=allow_unsafe
            )
            del cfg[BASE_KEY]

            merge_a_into_b(cfg, base_cfg)
            return base_cfg
        return cfg

def merge_from_file(self, cfg_filename: str, allow_unsafe: bool = False):
        """
        Merge configs from a given yaml file.

        Args:
            cfg_filename: the file name of the yaml config.
            allow_unsafe: whether to allow loading the config file with
                `yaml.unsafe_load`.
        """
        loaded_cfg = CfgNode.load_yaml_with_base(
            cfg_filename, allow_unsafe=allow_unsafe
        )
        loaded_cfg = type(self)(loaded_cfg)
        self.merge_from_other_cfg(loaded_cfg)