code: public BitSet projectG2(BitSet set) {
          BitSet projection = new BitSet(secondGraphSize);
          RNode xNode = null;
  
          for (int x = set.nextSetBit(0); x >= 0; x = set.nextSetBit(x + 1)) {
              xNode = (RNode) graph.get(x);
              projection.set(xNode.rMap.id2);
          }
          return projection;
      }
docs: Projects a RGraph bitset on the source graph G2.
  @param  set  RGraph BitSet to project
  @return      The associate BitSet in G2