code: @Override
      public int getIsotopeCount(IIsotope isotope) {
          int count = 0;
          Iterator<IMolecularFormula> componentIterator = components.iterator();
          while (componentIterator.hasNext()) {
              count += componentIterator.next().getIsotopeCount(isotope);
          }
          return count;
      }
docs: Checks a set of Nodes for the occurrence of the isotope in the
  adduct formula from a particular isotope. It returns 0 if the does not exist.
  
  @param   isotope          The IIsotope to look for
  @return                   The occurrence of this isotope in this adduct
  @see                      #getIsotopeCount()