code: def resize_pane(pymux, variables):
      
      try:
          left = int(variables['<left>'] or 0)
          right = int(variables['<right>'] or 0)
          up = int(variables['<up>'] or 0)
          down = int(variables['<down>'] or 0)
      except ValueError:
          raise CommandException('Expecting an integer.')
  
      w = pymux.arrangement.get_active_window()
  
      if w:
          w.change_size_for_active_pane(up=up, right=right, down=down, left=left)
  
          # Zoom in/out.
          if variables['-Z']:
              w.zoom = not w.zoom
docs: Resize/zoom the active pane.