docs: def customization(self):
          """
          Get a customization object representing the customization of the activity.
  
          .. versionadded:: 1.11
  
          :return: An instance of :class:`customization.ExtCustomization`
  
          Example
          -------
          >>> activity = project.activity(name='Customizable activity')
          >>> customization = activity.customization()
          >>> part_to_show = project.part(name='Bike')
          >>> customization.add_property_grid_widget(part_to_show, custom_title="My super bike"))
  
          """
          from .customization import ExtCustomization
  
          # For now, we only allow customization in an Ext JS context
          return ExtCustomization(activity=self, client=self._client)