TypeError at / 'NoneType' object is not callable

this is the code. kindly tell me what i'm doing wrong ...

def allowed_users(allowed_roles=[]): def decorator(view_func): def wrapper_func(request, *args, **kwargs):

        group = None
        if request.user.groups.exists():
            group = request.user.groups.all()[0].name

        if group in allowed_roles:
            return view_func(request, *args, **kwargs)
        else:
            return HttpResponse('You are not authorized to view this page')
    return wrapper_func
return decorator

def admin_only(view_func): def wrapper_function(request, *args, **kwargs): group = None

    if request.user.groups.exists():
        group = request.user.groups.all()[0].name

    if group == 'customer':
        return redirect('user-page')

    if group == 'admin':
        return view_func(request, *args, **kwargs)

    return wrapper_function