query: SELECT
    (wd:Q2481549 as ?item) 
    ("only project linked" as ?legend) 
    (GROUP_CONCAT(?group;separator = ",") as ?labels) 
    (GROUP_CONCAT(?count;separator = ",") as ?values)
  WHERE
  {
     SELECT *
     {
        SELECT ?group (COUNT(DISTINCT ?p) as ?count)
        {
          hint:Query hint:optimizer "None".
          ?p wdt:P1343 wd:Q665807 ; wikibase:sitelinks 1 .
          [] schema:about ?p ; schema:isPartOf ?ws . 
          ?wp wdt:P856 ?ws ; wdt:P1800 ?group .
          ?p wdt:P31 wd:Q5 .
        }
        GROUP BY ?group
        ORDER BY DESC(?count)
        LIMIT 15
     }
     ORDER BY DESC(?count) 
  }