code: def install_tab_event_filter(self, value):
          
          dock_tabbar = None
          tabbars = self.main.findChildren(QTabBar)
          for tabbar in tabbars:
              for tab in range(tabbar.count()):
                  title = tabbar.tabText(tab)
                  if title == self.title:
                      dock_tabbar = tabbar
                      break
          if dock_tabbar is not None:
              self.dock_tabbar = dock_tabbar
              # Install filter only once per QTabBar
              if getattr(self.dock_tabbar, 'filter', None) is None:
                  self.dock_tabbar.filter = TabFilter(self.dock_tabbar,
                                                      self.main)
                  self.dock_tabbar.installEventFilter(self.dock_tabbar.filter)
docs: Install an event filter to capture mouse events in the tabs of a
          QTabBar holding tabified dockwidgets.