How to use the makefun.main.SourceUnavailable function in makefun

if not isinstance(target, FunctionType):
        raise UnsupportedForCompilation("Only functions can be compiled by this decorator")

    if _evaldict is None or _evaldict is True:
        if _evaldict is True:
            frame = _get_callerframe(offset=1)
        else:
            frame = _get_callerframe()
        _evaldict, _ = extract_module_and_evaldict(frame)

    # first make sure that source code is available for compilation
    try:
        lines = getsource(target)
    except (OSError, IOError) as e:
        if 'could not get source code' in str(e):
            raise SourceUnavailable(target, e)
        else:
            raise

    # compile all references first
    try:
        # python 3
        func_closure = target.__closure__
        func_code = target.__code__
    except AttributeError:
        # python 2
        func_closure = target.func_closure
        func_code = target.func_code

    # Does not work: if `self.i` is used in the code, `i` will appear here
    # if func_code is not None:
    #     for name in func_code.co_names: