def merge_from_file(self, cfg_filename: str, allow_unsafe: bool = True) -> None:
        """
        Load content from the given config file and merge it into self.

        Args:
            cfg_filename: config filename
            allow_unsafe: allow unsafe yaml syntax
        """
        assert PathManager.isfile(cfg_filename), f"Config file '{cfg_filename}' does not exist!"
        loaded_cfg = self.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 object of latest version!"

        logger = logging.getLogger(__name__)

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

            loaded_ver = guess_version(loaded_cfg, cfg_filename)
        assert loaded_ver <= self.VERSION, "Cannot merge a v{} config into a v{} config.".format(
            loaded_ver, self.VERSION
        )

        if loaded_ver == self.VERSION:
            self.merge_from_other_cfg(loaded_cfg)
        else:
            # compat.py needs to import CfgNode
            from .compat import upgrade_config, downgrade_config

            logger.warning(
                "Loading an old v{} config file '{}' by automatically upgrading to v{}. "
                "See docs/CHANGELOG.md for instructions to update your files.".format(
                    loaded_ver, cfg_filename, self.VERSION
                )
            )
            # To convert, first obtain a full config at an old version
            old_self = downgrade_config(self, to_version=loaded_ver)
            old_self.merge_from_other_cfg(loaded_cfg)
            new_config = upgrade_config(old_self)
            self.clear()
            self.update(new_config)

        Load content from the given config file and merge it into self.

        Args:
            cfg_filename: config filename
            allow_unsafe: allow unsafe yaml syntax
        
video_chat_text/video_chat_with_StableLM/models/grit_src/third_party/CenterNet2/detectron2/config/config.py