of -1 lets the underlying movie encoder select the bitrate.

        extra_args : list of str or None, optional
            Extra command-line arguments passed to the underlying movie
            encoder.  The default, None, means to use
            :rc:`animation.[name-of-encoder]_args` for the builtin writers.

        metadata : dict[str, str], default: {}
            Dictionary of keys and values for metadata to include in
            the output file. Some keys that may be of use include:
            title, artist, genre, subject, copyright, srcform, comment.

        extra_anim : list, default: []
            Additional `Animation` objects that should be included
            in the saved movie file. These need to be from the same
            `.Figure` instance. Also, animation frames will
            just be simply combined, so there should be a 1:1 correspondence
            between the frames from the different animations.

        savefig_kwargs : dict, default: {}
            Keyword arguments passed to each `~.Figure.savefig` call used to
            save the individual frames.

        progress_callback : function, optional
            A callback function that will be called for every frame to notify
            the saving progress. It must have the signature ::

                def func(current_frame: int, total_frames: int) -> Any

            where *current_frame* is the current frame number and
            *total_frames* is the total number of frames to be saved.
            *total_frames* is set to None, if the total number of frames can
            not be determined. Return values may exist but are ignored.

            Example code to write the progress to stdout::

                progress_callback = lambda i, n: print(f'Saving frame {i}/{n}')

        Notes
        -----
        *fps*, *codec*, *bitrate*, *extra_args* and *metadata* are used to
        construct a `.MovieWriter` instance and can only be passed if
        *writer* is a string.  If they are passed as non-*None* and *writer*
        is a `.MovieWriter`, a `RuntimeError` will be raised.
        Nc