code: def prune_to_ingroup(self):
          
          # Prune to just the ingroup
          if not self._ingroup_node_id:
              _LOG.debug('No ingroup node was specified.')
              self._ingroup_node_id = self.root_node_id
          elif self._ingroup_node_id != self.root_node_id:
              self._do_prune_to_ingroup()
              self.root_node_id = self._ingroup_node_id
          else:
              _LOG.debug('Ingroup node is root.')
          return self.root_node_id
docs: Remove nodes and edges from tree if they are not the ingroup or a descendant of it.