code: public static String getPeptideSequenceFromNotation(HELM2Notation helm2notation) throws HELM2HandledException,
  			PeptideUtilsException, org.helm.notation2.exception.NotationException, ChemistryException {
  		List<PolymerNotation> polymers = helm2notation.getListOfPolymers();
  		StringBuffer sb = new StringBuffer();
  		for (PolymerNotation polymer : polymers) {
  			sb.append(PeptideUtils.getSequence(polymer) + " ");
  
  		}
  		sb.setLength(sb.length() - 1);
  		return sb.toString();
  	}
docs: method to get for all peptides the sequence
  
  @param helm2notation
  HELM2Notation
  @return rna sequences divided by white space
  @throws HELM2HandledException
  if the polymer contains HELM2 features
  @throws PeptideUtilsException
  if the polymer is not a peptide
  @throws org.helm.notation2.exception.NotationException if notation is not valid
  @throws ChemistryException
  if the Chemistry Engine can not be initialized