def is_subset(l1: list, l2: list) -> bool:
    """
    Test if l2 is a subset of l1, i.e. all elements of l2 are contained in l1 and return True if it the case, False
    otherwise.

    :param l1: main list
    :param l2: list whose elements are to be checked (if they're in l1 or not)
    :return: True if l2 is a subset of l1, False otherwise.
    """
    set1 = set(l1)
    set2 = set(l2)
    return set1.issubset(set2)