if lang is None:
        return None
    lang = lang.lower()
    return lang


def complete_existing_lang(incomplete: str):
    lang_path: Path
    for lang_path in get_lang_paths():
        if lang_path.is_dir() and lang_path.name.startswith(incomplete):
            yield lang_path.name


@app.callback()
def callback() -> None:
    if is_mkdocs_insiders():

        html += f"{json.dumps(key)}: {json.dumps(jsonable_encoder(value))},\n"

    if oauth2_redirect_url:
        html += f"oauth2RedirectUrl: window.location.origin + '{oauth2_redirect_url}',"

    html += """
    presets: [
        SwaggerUIBundle.presets.apis,
        SwaggerUIBundle.SwaggerUIStandalonePreset
        ],
    })"""

    if init_oauth:
        html += f"""