code: private IBond getNextBondWithUnplacedRingAtom() {
          for (IBond bond : molecule.bonds()) {
              IAtom beg = bond.getBegin();
              IAtom end = bond.getEnd();
              if (beg.getPoint2d() != null && end.getPoint2d() != null) {
                  if (end.getFlag(CDKConstants.ISPLACED) && !beg.getFlag(CDKConstants.ISPLACED) && beg.isInRing()) {
                      return bond;
                  }
                  if (beg.getFlag(CDKConstants.ISPLACED) && !end.getFlag(CDKConstants.ISPLACED) && end.isInRing()) {
                      return bond;
                  }
              }
          }
          return null;
      }
docs: Returns the next bond with an unplaced ring atom
  
  @return the next bond with an unplaced ring atom