code: public JTSLineStringExpression<?> exteriorRing() {
          if (exteriorRing == null) {
              exteriorRing = JTSGeometryExpressions.lineStringOperation(SpatialOps.EXTERIOR_RING, mixin);
          }
          return exteriorRing;
      }
docs: Returns the exterior ring of this Polygon.
  
  @return exterior ring