code: def create(self):
          
          self.idx_chan = QComboBox()
          self.idx_chan.activated.connect(self.display_window)
  
          self.idx_fig = QGraphicsView(self)
          self.idx_fig.scale(1, -1)
  
          layout = QVBoxLayout()
          layout.addWidget(self.idx_chan)
          layout.addWidget(self.idx_fig)
          self.setLayout(layout)
  
          self.resizeEvent(None)
docs: Create empty scene for power spectrum.