code: def focus_next(self, count=1):
          " Focus the next pane. "
          panes = self.panes
          if panes:
              self.active_pane = panes[(panes.index(self.active_pane) + count) % len(panes)]
          else:
              self.active_pane = Nonf focus_next(self, count=1):
          " Focus the next pane. "
          panes = self.panes
          if panes:
              self.active_pane = panes[(panes.index(self.active_pane) + count) % len(panes)]
          else:
              self.active_pane = None
docs: Focus the next pane.