query: SELECT ?item ?group ?elected ?start ?end ?cause
    WHERE { 
      ?item p:P39 ?ps . 
      ?ps ps:P39 wd:Q61937786 ; pq:P2937 wd:Q61946691 .
      OPTIONAL { ?ps pq:P580 ?start } .
      OPTIONAL { ?ps pq:P582 ?end }  .
      OPTIONAL { ?ps pq:P4100 ?group } .
      OPTIONAL { ?ps pq:P2715 ?elected } .
      OPTIONAL { ?ps pq:P1534 ?cause } .
   }