code: private static StringBuilder generateComplement(PolymerNotation polymer)
  			throws HELM2HandledException, RNAUtilsException, ChemistryException {
  		initComplementMap();
  		String sequence = getNaturalAnalogSequence(polymer);
  		StringBuilder sb = new StringBuilder();
  		for (char c : sequence.toCharArray()) {
  			sb.append(complementMap.get(String.valueOf(c)));
  		}
  		return sb;
  	}
docs: method to generate the complement sequence for a rna/dna polymer
  
  @param polymer
  PolymerNotation
  @return complement sequence saved in StringBuilder
  @throws HELM2HandledException
  if the polymer contains HELM2 features
  @throws RNAUtilsException
  if the polymer is not RNA or DNA
  @throws ChemistryException
  if the Chemistry Engine can not be initialized