presto-geospatial/src/main/java/io/prestosql/plugin/geospatial/aggregation/ConvexHullAggregation.java/ConvexHullAggregation/output
class ConvexHullAggregation:    @OutputFunction(GEOMETRY_TYPE_NAME)
    public static void output(@AggregationState GeometryState state, BlockBuilder out)
    {
        if (state.getGeometry() == null) {
            out.appendNull();
        }
        else {
            GEOMETRY.writeSlice(out, GeometrySerde.serialize(state.getGeometry()));
        }
    }