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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def admin_tools_render_menu_css(context, menu=None):
 """ Template tag that renders the menu css files,, it takes an optional ``Menu`` instance as unique argument, if not given, the menu will be retrieved with the ``get_admin_menu`` function. """

    if menu is None:
        menu = get_admin_menu(context)

    context.update({
        'template': 'admin_tools/menu/css.html',
        'css_files': menu.Media.css,
    })
    return context