code: def mk_dropdown_tree(cls, model, root_node, for_node=None):
          '''
          Override of ``treebeard`` method to enforce the same root.
          '''
          options = []
          # The difference is that we only generate the subtree for the current root.
          logger.debug("Using root node pk of %s" % root_node.pk)
          cls.add_subtree(for_node, root_node, options)
          return options[1:f mk_dropdown_tree(cls, model, root_node, for_node=None):
          '''
          Override of ``treebeard`` method to enforce the same root.
          '''
          options = []
          # The difference is that we only generate the subtree for the current root.
          logger.debug("Using root node pk of %s" % root_node.pk)
          cls.add_subtree(for_node, root_node, options)
          return options[1:]
docs: Override of ``treebeard`` method to enforce the same root.