code: public static String getNucleotideSequenceFromNotation(HELM2Notation helm2notation)
  			throws NotationException, NucleotideLoadingException, HELM2HandledException, ChemistryException {
  		List<PolymerNotation> polymers = helm2notation.getListOfPolymers();
  		StringBuffer sb = new StringBuffer();
  		for (PolymerNotation polymer : polymers) {
  			try {
  				sb.append(RNAUtils.getNucleotideSequence(polymer) + " ");
  			} catch (RNAUtilsException e) {
  				e.printStackTrace();
  				throw new NotationException("Input complex notation contains non-nucleic acid polymer");
  			}
  		}
  		sb.setLength(sb.length() - 1);
  		return sb.toString();
  	}
docs: method to get for all rna/dnas the nucleotide sequence form an
  HELM2Notation
  
  @param helm2notation
  input HELM2Notation
  @return rna/dna nucleotide sequences divided with white space
  @throws NucleotideLoadingException if nucleotides can not be loaded
  @throws NotationException if notation is not valid
  @throws HELM2HandledException
  if HELM2 features are involved
  @throws ChemistryException if chemistry engine can not be initialized