How to fix an error in the wolf, goat and cabbage problem in prolog?

Question

Prolog

There is a known task: A farmer has a wolf, a goat and a cabbage. All of them are located on the left bank of the river. It is necessary to transport this "trio" to the right bank, but one thing can fit in the boat - a wolf, a goat or a cabbage. You can not leave a wolf with a goat and a goat with cabbage on the same bank.
Solution taken from here: https://pro-prof.com/archives/1299

check(L):-
  member(wolf, L), !, not(member(goat, L));
  member(goat, L), !, not(member(cabbage, L));
  !.
generate((Left, Right, left)):-
  permutation_length(Left, 1, LeftPart),
  subtraction(Left, LeftPart, NewLeft),
  append(LeftPart, Right, NewRight),
  check(NewLeft),
  not(edge(_, (NewLeft, NewRight, right))),
  assert(edge((Left, Right, left), (NewLeft, NewRight, right))),
  fail;!.
generate((Left, Right, right)):-
  permutation_length(Right, 1, RightPart),
  subtraction(Right, RightPart, NewRight),
  append(RightPart, Left, NewLeft),
  check(NewRight),
  not(edge(_, (NewLeft, NewRight, left))),
  assert(edge((Left, Right, right), (NewLeft, NewRight, left))),
  fail;!.

path(Finish, [[Finish | PathPart] | _], [Finish | PathPart]):-!.
path(Finish, [[X | PathPart] | ProcList], Path):-
  generate(X),
  findall(Y, step(X, PathPart, Y), AdjNodes),
  append(ProcList, AdjNodes, NewProcList), !,
  path(Finish, NewProcList, Path).
step(X,T,[Y,X|T]):-
  edge(X,Y),
  not(member(Y,T)).
path(Start, Finish):-
    path(Finish, [[Start]], RPath), !,
    reverse(RPath,Path), write(Path).

Condition:

path(([wolf, goat, cabbage], [], left), ([], _, right)).

I'm trying to run the code exactly as described in the example, but an error is displayed:

How to define the permutation_length function?