code: @Override
      public boolean contains(IIsotope isotope) {
          for (IIsotope thisIsotope : isotopes()) {
              if (isTheSame(thisIsotope, isotope)) {
                  return true;
              }
          }
          return false;
      }
docs: True, if the MolecularFormula contains the given IIsotope object and not
  the instance. The method looks for other isotopes which has the same
  symbol, natural abundance and exact mass.
  
  @param  isotope  The IIsotope this MolecularFormula is searched for
  @return          True, if the MolecularFormula contains the given isotope object