code: private List<IIsotope> isotopesList() {
          List<IIsotope> isotopes = new ArrayList<IIsotope>();
          Iterator<IMolecularFormula> componentIterator = components.iterator();
          while (componentIterator.hasNext()) {
              Iterator<IIsotope> compIsotopes = componentIterator.next().isotopes().iterator();
              while (compIsotopes.hasNext()) {
                  IIsotope isotope = compIsotopes.next();
                  if (!isotopes.contains(isotope)) {
                      isotopes.add(isotope);
                  }
              }
          }
          return isotopes;
      }
docs: Returns a List for looping over all isotopes in this adduct formula.
  
  @return    A List with the isotopes in this adduct formula