code: private List<Integer> getBondNosForRingGroup(IAtomContainer molecule, List<Integer> ringGroup, IRingSet ringSet) {
          List<Integer> btc = new ArrayList<Integer>();
          for (Integer i : ringGroup) {
              for (IBond bond : ringSet.getAtomContainer(i).bonds()) {
                  if (btc.size() > 0) {
                      if (!btc.contains(molecule.indexOf(bond))) {
                          btc.add(molecule.indexOf(bond));
                      }
                  } else {
                      btc.add(molecule.indexOf(bond));
                  }
              }
          }
          return btc;
      }
docs: Gets the List of bond nos corresponding to a particular set of fused rings.
  
  @param {@link IAtomContainer} molecule
  @param ringGroup
  @param {@link IRingSet} ringSet
  @return List of bond numbers for each set