code: def move_tab(self, index_from, index_to):
          
          filename = self.filenames.pop(index_from)
          editor = self.editors.pop(index_from)
  
          self.filenames.insert(index_to, filename)
          self.editors.insert(index_to, editor)
docs: Move tab.
  
          (tabs themselves have already been moved by the history.tabwidget)