Establishes a connection to the ffmpeg writer

        Parameters
        ----------
        filename : str
            Filename of the movie to open.  Filename should end in mp4,
            but other filetypes may be supported.  See "imagio.get_writer"

        framerate : int, optional
            Frames per second.

def open_movie(self, filename, framerate=24):
        """
        Establishes a connection to the ffmpeg writer

        Parameters
        ----------
        filename : str
            Filename of the movie to open.  Filename should end in mp4,
            but other filetypes may be supported.  See "imagio.get_writer"

        framerate : int, optional
            Frames per second.

        """
        if isinstance(vtki.FIGURE_PATH, str) and not os.path.isabs(filename):
            filename = os.path.join(vtki.FIGURE_PATH, filename)
        self.mwriter = imageio.get_writer(filename, fps=framerate)