code: @Override
  	public void addChain(Chain chain, int modelnr) {
  		// if model has not been initialized, init it!
  		chain.setStructure(this);
  		if (models.isEmpty()) {
  			Model model = new Model();
  			List<Chain> modelChains = new ArrayList<>() ;
  			modelChains.add(chain);
  			model.setChains(modelChains);
  			models.add(model);
  
  		} else {
  			Model model = models.get(modelnr);
  			model.addChain(chain);
  		}
  
  
  
  	}
docs: {@inheritDoc}