static isSupersetOf(setA, setB) {
    for (var element of setB) {
      if (!setA.has(element)) {
        return false;
      }
    }

    return true;
  }
Checks whether or not a set (setA) is a superset of another set (setB).

@param {Set<Number>} setA A set.
@param {Set<Number>} setB A set.
@returns {Boolean} A boolean indicating whether or not setB is a superset of setA.