code: def set_widget(self, jp_imgw):
          
          super(ImageViewEvent, self).set_widget(jp_imgw)
  
          self.jp_evt = EventListener(source=jp_imgw)
          self.jp_evt.watched_events = [
              'keydown', 'keyup', 'mouseenter', 'mouseleave',
              'mousedown', 'mouseup', 'mousemove', 'wheel',
              'contextmenu'
          ]
          self.jp_evt.prevent_default_action = True
  
          self.jp_evt.on_dom_event(self._handle_event)
          self.logger.info("installed event handlers")
  
          return self.make_callback('map')
docs: Call this method with the Jupyter image widget (image_w)
          that will be used.