code: public JTSLineStringExpression<LineString> interiorRingN(int idx) {
          return JTSGeometryExpressions.lineStringOperation(SpatialOps.INTERIOR_RINGN, mixin, ConstantImpl.create(idx));
      }
docs: Returns the N th interior ring for this Polygon as a LineString.
  
  @param idx one based index
  @return interior ring at index