code: function HasManyThrough(model, related, through, firstKey, secondKey, localKey, secondLocalKey) {
          var _this = _super.call(this, model) /* istanbul ignore next */ || this;
          _this.related = _this.model.relation(related);
          _this.through = _this.model.relation(through);
          _this.firstKey = firstKey;
          _this.secondKey = secondKey;
          _this.localKey = localKey;
          _this.secondLocalKey = secondLocalKey;
          return _this;
      }
docs: Create a new has many through instance.