请告诉我第53行代码有什么问题？据我所知，它应该返回{[{12456}，{77777}，{99999}，{88888}]，[]}。为什么不匹配？如何修复？谢谢！

fu() ->
Tr = [{12456},{77777}, {99999}, {88888}],
car:foa1(Tr, {[],[]}).

foa1([], Acc) -> Acc;

foa1([{Tr}|Ot], {A1,A2}) ->
Direction = unknown,
A = fun(T, {Acc1, Acc2}) ->
case Direction of
unknown -> {[T | Acc1], Acc2};
_ -> {Acc1, [T | Acc2]}
end
end,
{Acc1, Acc2} =  lists:foldl(A, {[],[]}, Tr),
foa1 (Ot, {A1 ++Acc1,  A2 ++ Acc2}).

**异常错误：函数<car.0.18093156>car：foa 1/2（car.erl，第53行）中没有与list：foldl（#Fun，{[]，[]}，12456）（lists.erl，第1262行）匹配的函数子句