def flatten_lists(*lists):
    """Flatten several lists into one list.

    Examples
    --------
    >>> flatten_lists([0, 1, 2], [3, 4, 5])
    [0, 1, 2, 3, 4, 5]

    Parameters
    ----------
    lists : an arbitrary number of iterable collections
        The type of the collections is not limited to lists,
        they can also be sets, tuples, etc.

    Returns
    -------
    flat_list : a flattened list
    """
    return [x for sublist in lists for x in sublist]