code: def get_next_instance(self, obj):
          
          ordered_siblings = obj.get_siblings().filter(placeholder=obj.placeholder).order_by('position')
          pos = list(ordered_siblings).index(obj.cmsplugin_ptr)
          if pos < ordered_siblings.count() - 1:
              next_sibling = ordered_siblings[pos + 1]
              return next_sibling.get_bound_plugin()
docs: Return the next plugin instance for the given object.
          This differs from `obj.get_next_sibling()` which returns an unsorted sibling.