How to use the mkdocs.utils.get_relative_url function in mkdocs

def get_context(nav, files, config, page=None, base_url=''):
    """
    Return the template context for a given page or template.
    """

    if page is not None:
        base_url = utils.get_relative_url('.', page.url)

    extra_javascript = utils.create_media_urls(config['extra_javascript'], page, base_url)

    extra_css = utils.create_media_urls(config['extra_css'], page, base_url)

    # Support SOURCE_DATE_EPOCH environment variable for "reproducible" builds.
    # See https://reproducible-builds.org/specs/source-date-epoch/
    timestamp = int(os.environ.get('SOURCE_DATE_EPOCH', timegm(datetime.utcnow().utctimetuple())))

    return {
        'nav': nav,
        'pages': files.documentation_pages(),

        'base_url': base_url,

        'extra_css': extra_css,

"""

    # Run `pre_template` plugin events.
    template = config['plugins'].run_event(
        'pre_template', template, template_name=name, config=config
    )

    if utils.is_error_template(name):
        # Force absolute URLs in the nav of error pages and account for the
        # possability that the docs root might be different than the server root.
        # See https://github.com/mkdocs/mkdocs/issues/77.
        # However, if site_url is not set, assume the docs root and server root
        # are the same. See https://github.com/mkdocs/mkdocs/issues/1598.
        base_url = urlparse(config['site_url'] or '/').path
    else:
        base_url = utils.get_relative_url('.', name)

    context = get_context(nav, files, config, base_url=base_url)

    # Run `template_context` plugin events.
    context = config['plugins'].run_event(
        'template_context', context, template_name=name, config=config
    )

    output = template.render(context)

    # Run `post_template` plugin events.
    output = config['plugins'].run_event(
        'post_template', output, template_name=name, config=config
    )

    return output

def url_relative_to(self, other):
        """ Return url for file relative to other file. """
        return utils.get_relative_url(self.url, other.url if isinstance(other, File) else other)