code: def _bufferlist_overlay_visible(editor):
      
      @Condition
      def overlay_is_visible():
          app = get_app()
  
          text = editor.command_buffer.text.lstrip()
          return app.layout.has_focus(editor.command_buffer) and (
                  any(text.startswith(p) for p in ['b ', 'b! ', 'buffer', 'buffer!']))
      return overlay_is_visible
docs: True when the buffer list overlay should be displayed.
      (This is when someone starts typing ':b' or ':buffer' in the command line.)