def flatten_list(list_of_lists):
    """ Will convert a list of lists in a list with the items inside each sub-list.

    Parameters
    ----------
    list_of_lists: list[list[object]]

    Returns
    -------
    list
    """
    if not list_of_lists:
        return []

    if isinstance(list_of_lists[0], list):
        lst = []
        for l in list_of_lists:
            lst.extend(l)
        return lst
    return list_of_lists