def flatten(list_of_lists: list) -> list:
    """Helper function to flat a list out of lists

    Args:
        list_of_lists (list): [description]

    Returns:
        list: [description]
    """
    flat_list = []
    for sublist in list_of_lists:
        for item in sublist:
            flat_list.append(item)
    return flat_list