def open_gif(self, filename):
        """
        Open a gif file.

        Parameters
        ----------
        filename : str
            Filename of the gif to open.  Filename must end in gif.

        """
        if filename[-3:] != 'gif':
            raise Exception('Unsupported filetype.  Must end in .gif')
        if isinstance(vtki.FIGURE_PATH, str) and not os.path.isabs(filename):
            filename = os.path.join(vtki.FIGURE_PATH, filename)
        self._gif_filename = os.path.abspath(filename)
        self.mwriter = imageio.get_writer(filename, mode='I')
Open a gif file.

        Parameters
        ----------
        filename : str
            Filename of the gif to open.  Filename must end in gif.