mission idea "Wolf Goat Cabbage "

Perhaps CheckiO should not have Fox, goose and bag of beans puzzle mission yet.

How about implementing the solution in Python?

specification:

wolf_goat_cabbage(purchases, ng_list) == [go1, return1, go2, return2,...]

example:

wolf_goat_cabbage({'wolf', 'goat', 'cabbage'}, [{'wolf', 'goat'}, {'goat', 'cabbage'}])
    == ['goat', '', 'cabbage', 'goat', 'wolf', '', 'goat']

initial code:

def wolf_goat_cabbage(purchases, ng_list):

    return []

if __name__ == '__main__':
    def checker(solution, purchases, ng_list, min_len):
        answer = solution(purchases, ng_list)

        if not isinstance(answer, list):
            print('wrong data type :', answer)
            return False

        dif = set(answer) - (purchases | {''})
        if dif:
            print('wrong cargo :', dif)
            return False

        if len(answer) > min_len:
            print(f'too much steps : {len(answer)} > {min_len}')
            return False

        if not (answer or min_len):
            return True

        bank_a, bank_b = purchases | {''}, set()
        for i, p in enumerate(answer):
            p = {p, ''}
            bank_a = bank_a | p if i % 2 else bank_a - p
            bank_b = bank_b - p if i % 2 else bank_b | p
            if bank_a in ng_list:
                print(f'you failed : {bank_a}')
                return False
            if bank_b in ng_list:
                print(f'you failed : {bank_b}')
                return False
        return not bank_a and bank_b == purchases | {''}

    assert checker(wolf_goat_cabbage, {'wolf', 'goat', 'cabbage'}, [{'wolf', 'goat'}, {'goat', 'cabbage'}], 7), 'two restriction'
    assert checker(wolf_goat_cabbage, {'wolf', 'goat', 'cabbage'}, [], 5), 'no restriction'
    assert checker(wolf_goat_cabbage, {'wolf', 'goat', 'cabbage'}, [{'wolf', 'goat'}], 5), 'one restriction'
    assert checker(wolf_goat_cabbage, {'wolf', 'goat', 'cabbage'},
                   [{'wolf', 'goat'}, {'goat', 'cabbage'}, {'wolf', 'cabbage'}], 0), 'three restriction'
    assert checker(wolf_goat_cabbage, {'fox', 'goose', 'bean'}, [{'fox', 'goose'}, {'goose', 'bean'}], 7), 'fox goose bean'