presto-geospatial/src/main/java/io/prestosql/plugin/geospatial/GeoFunctions.java/GeoFunctions/stBoundary
class GeoFunctions:    @Description("Returns the closure of the combinatorial boundary of this Geometry")
    @ScalarFunction("ST_Boundary")
    @SqlType(GEOMETRY_TYPE_NAME)
    public static Slice stBoundary(@SqlType(GEOMETRY_TYPE_NAME) Slice input)
    {
        OGCGeometry geometry = deserialize(input);
        if (geometry.isEmpty() && GeometryType.getForEsriGeometryType(geometry.geometryType()) == LINE_STRING) {
            // OCGGeometry#boundary crashes with NPE for LINESTRING EMPTY
            return EMPTY_MULTIPOINT;
        }
        return serialize(geometry.boundary());
    }