code: public void validateHELM(String helm) throws ValidationException, MonomerLoadingException, ChemistryException {
  		validate(helm);
  		setMonomerFactoryToDefault(helm);
  	}
docs: method to validate the input HELM-String
  
  @param helm
  input HELM-string
  @throws ValidationException
  if the input HELM is not valid
  @throws MonomerLoadingException
  if the MonomerFactory can not be refreshed
  @throws ChemistryException
  if the Chemistry Engine can not be initialized