code: public static PolymerNotation getComplement(PolymerNotation polymer)
  			throws RNAUtilsException,  ChemistryException, NucleotideLoadingException {
  		checkRNA(polymer);
  		PolymerNotation complementPolymer;
  		try {
  			complementPolymer = SequenceConverter.readRNA(generateComplement(polymer).toString()).getListOfPolymers()
  					.get(0);
  			complementPolymer = new PolymerNotation(complementPolymer.getPolymerID(),
  					complementPolymer.getPolymerElements(), "NormalComplement to " + polymer.getPolymerID().getId());
  			return complementPolymer;
  		} catch (NotationException | FastaFormatException | HELM2HandledException e) {
  			e.printStackTrace();
  			throw new RNAUtilsException("Complement polymer can not be built");
  		}
  
  	}
docs: method to get the normal complement polymer for a given rna/dna polymer
  @param polymer given polymernotation
  @return complement polymernotation of the given polymernotation
  @throws RNAUtilsException
  if the polymer is not rna or dna or the complement polymer
  can not be built
  @throws ChemistryException
  if the Chemistry Engine can not be initialized
  @throws NucleotideLoadingException if nucleotides can not be loaded