code: def repr(self, changed_widgets=None):
          
          if changed_widgets is None:
              changed_widgets={}
          return super(Widget, self).repr(changed_widgets)
docs: Represents the widget as HTML format, packs all the attributes, children and so on.
  
          Args:
              client (App): Client instance.
              changed_widgets (dict): A dictionary containing a collection of widgets that have to be updated.
                  The Widget that have to be updated is the key, and the value is its textual repr.