Flatten arbitrarily nested arrays

def recurs_flatten(lista):
    result = []
    for item in lista:
        if type(item) == type([]):
            result.extend(recurs_flatten(item))
        else:
            result.append(item)
    return result

# TESTS

def item(depth, value):
    if depth <= 1:
        return [value]
    else:
        return [item(depth - 1, value)]

def test_list(n):
    lista = []
    for i in range(n):
        if i == 0:
            lista.append(i)
        else:
            lista.append(item(i, i))
    return lista


generated_nested_list_a=test_list(9)
expected_flatten_list_a= [0,1,2,3,4,5,6,7,8]
print("test passed:"+ str(expected_flatten_list_a == recurs_flatten(generated_nested_list_a)))