code: @Override
      public IMolecularFormula addIsotope(IIsotope isotope, int count) {
          if (count == 0)
              return this;
          boolean flag = false;
          for (IIsotope thisIsotope : isotopes()) {
              if (isTheSame(thisIsotope, isotope)) {
                  isotopes.put(thisIsotope, isotopes.get(thisIsotope) + count);
                  flag = true;
                  break;
              }
          }
          if (!flag) {
              isotopes.put(isotope, count);
          }
  
          return this;
      }
docs: Adds an Isotope to this MolecularFormula in a number of occurrences.
  
  @param  isotope  The isotope to be added to this MolecularFormula
  @param  count    The number of occurrences to add
  @see             #addIsotope(IIsotope)