title: How to get movable graphical items inside a QGraphicsItemGroup?
body: <p>My goal is to write a software that displays two movable disks that live inside the same <code>QGraphicsItemGroup</code>. I'd like to use <code>QGraphicsItemGroup</code> because in this way each disk can access the position of the other. To make the objects movable, I use the flag <code>ItemIsMovable</code> which unfortunately doesn't seem to work inside a <code>QGraphicsItemGroup</code> The following program exemplifies my issue:</p>
  
  <pre><code>import sys
  from PyQt5.QtCore import Qt
  from PyQt5.QtWidgets import QGraphicsView, QGraphicsScene, QGraphicsItem,\ 
      QApplication, QGraphicsItemGroup, QGraphicsEllipseItem
  
  
  class MyDisk(QGraphicsEllipseItem):
      def __init__(self, top_left_x, top_left_y, radius, color):
          super().__init__(top_left_x, top_left_y, radius, radius)
          self.setBrush(color)
          self.setFlag(QGraphicsItem.ItemIsMovable)
  
  
  class MyGroup(QGraphicsItemGroup):
      def __init__(self):
          super().__init__()
          self.disk1 = MyDisk(50, 50, 20, Qt.red)
          self.disk2 = MyDisk(150, 150, 20, Qt.red)
          self.addToGroup(self.disk1)
          self.addToGroup(self.disk2)
          # self.setFlag(QGraphicsItemGroup.ItemIsMovable)
  
  
  class MyView(QGraphicsView):
      def __init__(self):
          super().__init__()
          self.scene = QGraphicsScene()
          self.setScene(self.scene)
          self.setWindowTitle('Red disks are not movable')
          self.setSceneRect(0, 0, 250, 250)
          self.group = MyGroup()
          self.scene.addItem(self.group)
          self.scene.addItem(MyDisk(150, 50, 20, Qt.green))
  
  
  if __name__ == '__main__':
      app = QApplication([])
      f = MyView()
      f.show()
      sys.exit(app.exec_())
  </code></pre>
  
  <p>My problem is that the green disk (not in the group) is movable but the two red disks (in the group) are not. How can I make the two red disks movable? Note that setting the flag <code>ItemIsMovable</code> inside <code>MyGroup</code> doesn't solve the problem because the red disks would then move together (you can try this by uncomment the comment in the code).</p>