code: public static String getNucleotideNaturalAnalogSequenceFromNotation(HELM2Notation helm2Notation)
  			throws NotationException, HELM2HandledException, ChemistryException {
  		List<PolymerNotation> polymers = helm2Notation.getListOfPolymers();
  		StringBuffer sb = new StringBuffer();
  		for (PolymerNotation polymer : polymers) {
  			try {
  				sb.append(RNAUtils.getNaturalAnalogSequence(polymer) + " ");
  			} catch (RNAUtilsException e) {
  				e.printStackTrace();
  				throw new NotationException("Input complex notation contains non-nucleid acid polymer");
  			}
  		}
  		sb.setLength(sb.length() - 1);
  		return sb.toString();
  	}
docs: method to generate for all rna polymers the natural analogue sequence
  
  @param helm2Notation
  input HELm2Notation
  @return natural analogue sequence(s)
  @throws NotationException
  if the input complex notation contains non-nucleid acid
  polymer(s)
  @throws HELM2HandledException
  if the polymer(s) contain(s) HELM2 features
  @throws ChemistryException
  if the Chemistry Engine can not be initialized