function _uniqContentEquals(aIterator, bIterator, stackA, stackB) {
    var a = _arrayFromIterator(aIterator);
    var b = _arrayFromIterator(bIterator);
    function eq(_a, _b) {
      return _equals(_a, _b, stackA.slice(), stackB.slice());
    }

    // if *a* array contains any element that is not included in *b*
    return !_includesWith(function (b, aItem) {
      return !_includesWith(eq, aItem, b);
    }, b, a);
  }
private _uniqContentEquals function.
That function is checking equality of 2 iterator contents with 2 assumptions
- iterators lengths are the same
- iterators values are unique

false-positive result will be returned for comparison of, e.g.
- [1,2,3] and [1,2,3,4]
- [1,1,1] and [1,2,3]