def find_index_of_subset(large_list, small_list):
    """
    Returns the index after the small_list within the large list,
    Returns None if not present.

    Adapted from https://stackoverflow.com/a/45819222 which shows that it is
    performant for input lengths < 1000, which is the common case for this function.
    """
    length_small_list = len(small_list)
    firstneedle = small_list[0]
    for idx, item in enumerate(large_list):
        if item == firstneedle:
            if large_list[idx : idx + length_small_list] == small_list:
                return idx + length_small_list
    return None