Python | Ошибка "TypeError: 'NoneType' object is not iterable"

def Task_3():
    choice = int(input("What scenario you want to start ([1] - Best-Case | [2] - Worst-Case): "))
    if choice == 1:
        start = time.time()
        sequence = random.sample(range(-65535, 65535), 4999)  # sequence
        to_find = random.randint(-65535, 65535)
        sequence_m = sequence.insert(0, to_find)
        for element in sequence_m:
            if element == to_find:
                print('Element {} was found on index {}. Stop searching'.format(to_find, sequence_m.index(element)))
                break  # comment if you want to continue searching
            else:
                print('Element {} was not found'.format(to_find))
                break
        end = time.time()
        print(f"Time taken: {(end - start) * 10 ** 3:.03f}ms")

def Task_3():
    choice = int(input("What scenario you want to start ([1] - Best-Case | [2] - Worst-Case): "))
    if choice == 1:
        start = time.time()
        sequence = random.sample(range(-65535, 65535), 4999)  # sequence
        to_find = random.randint(-65535, 65535)
        sequence.insert(0, to_find)
        for element in sequence:
            if element == to_find:
                print('Element {} was found on index {}. Stop searching'.format(to_find, sequence.index(element)))
                break  # comment if you want to continue searching
            else:
                print('Element {} was not found'.format(to_find))
                break
        end = time.time()
        print(f"Time taken: {(end - start) * 10 ** 3:.03f}ms")
 
Task_3()