code: def on_lstCanvasExpLayers_itemSelectionChanged(self):
          
          self.parent.exposure_layer = self.selected_canvas_explayer()
          lblText = self.parent.get_layer_description_from_canvas(
              self.parent.exposure_layer, 'exposure')
          self.lblDescribeCanvasExpLayer.setText(lblText)
          self.parent.pbnNext.setEnabled(True)
docs: Update layer description label
  
          .. note:: This is an automatic Qt slot
             executed when the category selection changes.