code: def addView(self, viewType):
          
          if not viewType:
              return None
          
          view = viewType.createInstance(self, self.viewWidget())
          self.addTab(view, view.windowTitle())
          return view
docs: Adds a new view of the inputed view type.
          
          :param      viewType | <subclass of XView>
          
          :return     <XView> || None