public LineStringExpression<LineString> interiorRingN(int idx) {
        return GeometryExpressions.lineStringOperation(SpatialOps.INTERIOR_RINGN, mixin, ConstantImpl.create(idx));
    }
Returns the N th interior ring for this Polygon as a LineString.

@param idx one based index
@return interior ring at index
querydsl-spatial/src/main/java/com/querydsl/spatial/PolygonExpression.java