code: def update_move_to_child_vars(self):
          
          newdepth = self.target.depth
          newpos = None
          siblings = []
          if self.pos in ('first-child', 'last-child', 'sorted-child'):
              # moving to a child
              parent = self.target
              newdepth += 1
              if self.target.is_leaf():
                  # moving as a target's first child
                  newpos = 1
                  self.pos = 'first-sibling'
                  siblings = get_result_class(self.node_cls).objects.none()
              else:
                  self.target = self.target.get_last_child()
                  self.pos = {
                      'first-child': 'first-sibling',
                      'last-child': 'last-sibling',
                      'sorted-child': 'sorted-sibling'}[self.pos]
  
              # this is not for save(), since if needed, will be handled with a
              # custom UPDATE, this is only here to update django's object,
              # should be useful in loops
              parent.numchild += 1
  
          return newdepth, siblings, newpos
docs: Update preliminar vars in :meth:`move` when moving to a child