query: SELECT (?class AS ?item) (COUNT(DISTINCT(?x)) AS ?count) WHERE {
     hint:Query hint:optimizer "None".
     ?ref pr:P687 ?p .
     ?stmt prov:wasDerivedFrom ?ref .
     ?x ?pred ?stmt .
     ?x wdt:P31 ?class .
  #   ?class wdt:P279* wd:Q732577 .
  }
  GROUP BY ?class ORDER BY DESC(?count)