code: def _set_clipper(self, node, clipper):
          
          if node in self._clippers:
              self.detach(self._clippers.pop(node))
          if clipper is not None:
              self.attach(clipper)
              self._clippers[node] = clipper
docs: Assign a clipper that is inherited from a parent node.
  
          If *clipper* is None, then remove any clippers for *node*.