def flatten_lists_of_lists(lists_of_lists):
    """
    Flatten list of lists into a list
    ex:
        [[1, 2], [3]] => [1, 2, 3]

    :param lists_of_lists: list(list(elems))
    :return: list(elems)
    """

    return [elem for sublist in lists_of_lists for elem in sublist]