class_docstr: Base class representing an object in a scene.
  
  A group of nodes connected through parent-child relationships define a 
  scenegraph. Nodes may have any number of children.
  
  Each Node defines a ``transform`` property, which describes the position,
  orientation, scale, etc. of the Node relative to its parent. The Node's
  children inherit this property, and then further apply their own
  transformations on top of that. 
  
  With the ``transform`` property, each Node implicitly defines a "local" 
  coordinate system, and the Nodes and edges in the scenegraph can be thought
  of as coordinate systems connected by transformation functions.
  
  Parameters
  ----------
  parent : Node
      The parent of the Node.
  name : str
      The name used to identify the node.
  transforms : instance of TransformSystem | None
      The associated transforms.
docstr: Parent change event handler
  
  Parameters
  ----------
  event : instance of Event
      The event.
docstr_tok: ["Parent","change","event","handler","Parameters","--","--","--","--","--","event",":","instance","of","Event","The","event","."]
code: def on_parent_change(self, event):
      """Parent change event handler
  
      Parameters
      ----------
      event : instance of Event
          The event.
      """
      self._scene_node = None
  
imports: from __future__ import division
  import weakref
  from contextlib import contextmanager
  from ..util.event import Event, EmitterGroup
  from ..visuals.transforms import NullTransform, BaseTransform, ChainTransform, create_transform, TransformSystem
label_desc: Use image node_id 20 for calling the Node obj's underlying member method code with example usage: obj.on_parent_change(event) without return types