pub fn contains(in set: Tree(a), this member: a) -> Bool

pub fn count(set: Tree(a)) -> Int

pub fn delete(from set: Tree(a), this member: a) -> Tree(a)

pub fn filter(
  in set: Tree(a),
  for property: fn(a) -> Bool,
) -> Tree(a)

pub fn fold(
  over set: Tree(a),
  from initial: b,
  with reducer: fn(b, a) -> b,
) -> b

pub fn from_list(
  members: List(a),
  compare: fn(a, a) -> Order,
) -> Tree(a)

pub fn insert(into set: Tree(a), this member: a) -> Tree(a)

pub fn intersection(
  of first: Tree(a),
  and second: Tree(a),
) -> Tree(a)

pub fn new(compare: fn(a, a) -> Order) -> Tree(a)

pub fn take(
  from set: Tree(a),
  keeping desired: List(a),
) -> Tree(a)

pub fn to_list(set: Tree(a)) -> List(a)

pub fn union(of first: Tree(a), and second: Tree(a)) -> Tree(a)