code: public static final int getTotalMonomerCount(HELM2Notation helm2notation) {
      int result = 0;
      for (PolymerNotation polymer : helm2notation.getListOfPolymers()) {
        result += PolymerUtils.getTotalMonomerCount(polymer);
      }
      return result;
    }
docs: method to get the total number of MonomerNotationUnits in a HELMNotation
  object
  @param helm2notation given HELM2Notation
  @return number of MonomerNotationUnits