function BucketMap() {
        var _ref2 = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : {},
            _ref2$arrays = _ref2.arrays,
            arrays = _ref2$arrays === void 0 ? false : _ref2$arrays;

        _classCallCheck(this, BucketMap);

        this.map = new Map();
        this[Symbol.iterator] = this.map[Symbol.iterator];
        this.arrays = arrays;
      }
Map that can hold multiple values per key