Make a self-edge on a vertex (a) If a1.attr1==a2.attr1

1 
CREATE QUERY CreateEdgesBetween2Vertices(/* Parameters here */) FOR GRAPH MyGraph { 
  MapAccum<STRING,VERTEX<a1>> @@mapV;
  seed(a1) = {a1.*};
  seed2(a2) ={a2.*};

  S1 = SELECT s FROM seed:s ACCUM @@mapV += (a1.attr1->s);
  
  S2 = SELECT tgt FROM seed2:tgt ACCUM 
        IF @@mapV.containsKey(tgt.attr1) THEN
          INSERT INTO MY_EDGE (FROM, TO) VALUES (@@mapV.get(tgt.attr1), tgt)
        END;
}