code: public UITab addTab(UITab tab, UIContainer container)
  	{
  		if (tab.isActive())
  			activeTab = tab;
  
  		add(tab);
  		tab.setContainer(container);
  		tab.setActive(false);
  		listTabs.put(tab, container);
  		updateSize();
  
  		if (attachedContainer != null)
  		{
  			setupTabContainer(container);
  			calculateTabPosition();
  		}
  		return tab;
  	}
docs: Adds a {@link UITab} and its corresponding {@link UIContainer} to this {@link UITabGroup}.<br>
  Also sets the width of this {@code UITabGroup}.
  
  @param tab tab to add to the UITabGroup
  @param container {@link UIContainer} linked to the {@link UITab}
  @return this {@link UITab}