PREFIX  rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX  rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
SELECT  ?b ?y
WHERE
    { ?b rdf:type rdf:Bag .
      ?b ?x ?y . 
      FILTER ( ! ( ( ?x = rdf:type ) && ( ?y = rdf:Bag ) ) ) .
    }