code: def init_layout(self):
          
          self.widget = QGraphicsProxyWidget(self.parent_widget())
          widget = self.widget
          for item in self.child_widgets():
              widget.setWidget(item)
              break
          super(QtGraphicsWidget, self).init_widget()
          super(QtGraphicsWidget, self).init_layout()
docs: Create the widget in the layout pass after the child widget has
          been created and intialized. We do this so the child widget does not
          attempt to use this proxy widget as its parent and because
          repositioning must be done after the widget is set.