def find_sublist_index(ls, sub_ls):
    """Find the index at which the sublist sub_ls can be found in ls.

    @type ls: list
    @type sub_ls: list

    @return: index of the matching location or None if no match can be made.
    """
    sub_length = len(sub_ls)
    for i in range(len(ls)):
        if ls[i:i + sub_length] == sub_ls:
            return i
    return None
