title: Removing icon and style of QMdiSubWindow
body: <p>I notice that windows from QMdiarea needs to be style customized. I want to remove icon which appears on topleft of QMdiSubWindow widget and at the same time change this ugly blue color of window to something which look pretty good.</p>
  <p>I have tried my setWindowsflag, but no effect.</p>
  <p><strong>The code:</strong></p>
  <pre><code>class Mywindow(QtWidgets.QMainWindow):
      def __init__(self, parent=None):
          super(Mywindow, self).__init__(parent)
          
          self.setMinimumSize(QtCore.QSize(800,600))
          self.setWindowTitle('Customized style')
          self.mdiarea = QtWidgets.QMdiArea()
          self.setCentralWidget(self.mdiarea)
          self.mdiarea.setWindowTitle('Test')
          
          self.window = QtWidgets.QWidget()        
          self.mdiarea.addSubWindow(self.window)
  
  if __name__ == '__main__':
      import sys
  
      app = QtWidgets.QApplication(sys.argv)
      app.setStyle('Fusion')
      view = Mywindow()
      view.showMaximized()
      sys.exit(app.exec_())
  </code></pre>
  <p>Current Display:</p>
  <p><a href="https://i.stack.imgur.com/WE50r.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/WE50r.png" alt="enter image description here" /></a></p>
  <p>Wants to obtain:</p>
  <p><a href="https://i.stack.imgur.com/rMdoS.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/rMdoS.png" alt="enter image description here" /></a></p>
  <p>Any idea how to achieve that?</p>