def to_yaml(
            self,
            filename: Optional[Union[str, PathLike]] = None,
            default_flow_style: bool = False,
            encoding: str = "utf-8",
            errors: str = "strict",
            **yaml_kwargs,
        ):
            """
            Transform the BoxList object into a YAML string.

            :param filename:  If provided will save to file
            :param default_flow_style: False will recursively dump dicts
            :param encoding: File encoding
            :param errors: How to handle encoding errors
            :param yaml_kwargs: additional arguments to pass to yaml.dump
            :return: string of YAML or return of `yaml.dump`
            """
            return _to_yaml(
                self.to_list(),
                filename=filename,
                default_flow_style=default_flow_style,
                encoding=encoding,
                errors=errors,
                **yaml_kwargs,
            )

            Transform the BoxList object into a YAML string.

            :param filename:  If provided will save to file
            :param default_flow_style: False will recursively dump dicts
            :param encoding: File encoding
            :param errors: How to handle encoding errors
            :param yaml_kwargs: additional arguments to pass to yaml.dump
            :return: string of YAML or return of `yaml.dump`
            
box/box_list.py