presto-geospatial/src/main/java/io/prestosql/plugin/geospatial/GeoFunctions.java/GeoFunctions/stIsRing
class GeoFunctions:    @SqlNullable
    @Description("Returns TRUE if and only if the line is closed and simple")
    @ScalarFunction("ST_IsRing")
    @SqlType(BOOLEAN)
    public static Boolean stIsRing(@SqlType(GEOMETRY_TYPE_NAME) Slice input)
    {
        OGCGeometry geometry = deserialize(input);
        validateType("ST_IsRing", geometry, EnumSet.of(LINE_STRING));
        OGCLineString line = (OGCLineString) geometry;
        return line.isClosed() && line.isSimple();
    }