<gh_stars>1000+
def append(list1, list2):
    pass


def concat(lists):
    pass


def filter(function, list):
    pass


def length(list):
    pass


def map(function, list):
    pass


def foldl(function, list, initial):
    pass


def foldr(function, list, initial):
    pass


def reverse(list):
    pass

def append(list1, list2):
    pass


def concat(lists):
    pass


def filter(function, list):
    pass


def length(list):
    pass


def map(function, list):
    pass


def foldl(function, list, initial):
    pass


def foldr(function, list, initial):
    pass


def reverse(list):
    pass