Render a wavedrom image

def render_wavedrom(self, node, outpath, bname, format):
    """
    Render a wavedrom image
    """

    # Try to convert node, raise error with code on failure
    try:
        svgout = WaveDrom().renderWaveForm(0, json.loads(node['code']))
    except JSONDecodeError as e:
        raise SphinxError("Cannot render the following json code: \n{} \n\nError: {}".format(node['code'], e))

    if not os.path.exists(outpath):
        os.makedirs(outpath)

    # SVG can be directly written and is supported on all versions
    if format == 'image/svg+xml':
        fname = "{}.{}".format(bname, "svg")
        fpath = os.path.join(outpath, fname)
        svgout.saveas(fpath)
        return fname

    # It gets a bit ugly, if the output does not support svg. We use cairosvg, because it is the easiest
    # to use (no dependency on installed programs). But it only works for Python 3.
    try:
        import cairosvg
    except:
        raise SphinxError(__("Cannot import 'cairosvg'. In Python 2 wavedrom figures other than svg are "
                             "not supported, in Python 3 ensure 'cairosvg' is installed."))

    if format == 'application/pdf':
        fname = "{}.{}".format(bname, "pdf")
        fpath = os.path.join(outpath, fname)
        cairosvg.svg2pdf(svgout.tostring(), write_to=fpath)
        return fname

    if format == 'image/png':
        fname = "{}.{}".format(bname, "png")
        fpath = os.path.join(outpath, fname)
        cairosvg.svg2png(svgout.tostring(), write_to=fpath)
        return fname

    raise SphinxError("No valid wavedrom conversion supplied")