Project(Join(Project(Extend(Extend(AggregationJoin(Aggregation(??agg1: ?s, SAMPLE,
                                                   {},
                                                   G1=Group((?s),
                                                      BGP( ?s <http://example/label> ?label))),
                                                   Aggregation(??agg2: ?label, COUNT,
                                                   {}, G1)),
                                   ?s,
                                   ??agg1),
                            ?label_count,
                            ??agg2),
                     {?s, ?label_count}),
             BGP( ?s <http://example/p> ?o)),
        {?label_count, ?o, ?s})