CG_IsSolid — Test if the geometry is a solid. No validity check is performed.
boolean CG_IsSolid(geometry geom1);
Availability: 3.5.0
            
            This method needs SFCGAL backend.
        
            
            This function supports 3d and will not drop the z-index.
        
            
            This function supports Polyhedral surfaces.
        
            
            This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).