code: def add_external_path(self, path):
          
          if not osp.exists(path):
              return
          self.removeItem(self.findText(path))
          self.addItem(path)
          self.setItemData(self.count() - 1, path, Qt.ToolTipRole)
          while self.count() > MAX_PATH_HISTORY + EXTERNAL_PATHS:
              self.removeItem(EXTERNAL_PATHS)
docs: Adds an external path to the combobox if it exists on the file system.
          If the path is already listed in the combobox, it is removed from its
          current position and added back at the end. If the maximum number of
          paths is reached, the oldest external path is removed from the list.