code: def decorate_event_js(js_code):
      
      def add_annotation(method):
          setattr(method, "__is_event", True )
          setattr(method, "_js_code", js_code )
          return method
      return add_annotation
docs: setup a method as an event, adding also javascript code to generate
  
      Args:
          js_code (str): javascript code to generate the event client-side.
              js_code is added to the widget html as 
              widget.attributes['onclick'] = js_code%{'emitter_identifier':widget.identifier, 'event_name':'onclick'}