function setIntersection(set1, set2) {
  var intersection = lf.structs.set.create();
  set1.forEach(function(value) {
    if (set2.has(value)) {
      intersection.add(value);
    }
  });
  return intersection;
}
@param {!lf.structs.Set} set1
@param {!lf.structs.Set} set2
@return {!lf.structs.Set} The intersection of set1 and set2