old_contents: from django.db.models.signals import ModelSignal
  
  # Behaves like Djangos normal pre-/post_save signals signals with the
  # added arguments ``target`` and ``position`` that matches those of
  # ``move_to``.
  # If the signal is called from ``save`` it'll not be pass position.
  node_moved = ModelSignal(providing_args=[
      'instance',
      'target',
      'position'
  ])
  
new_contents: from django.db.models.signals import ModelSignal
  
  # Behaves like Djangos normal pre-/post_save signals signals with the
  # added arguments ``target`` and ``position`` that matches those of
  # ``move_to``.
  # If the signal is called from ``save`` it'll not be pass position.
  
  node_moved = ModelSignal(providing_args=[
      'instance',
      'target',
      'position'
  ])
  
subject: Update signals.py