<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def on_lstLayerModes_itemSelectionChanged(self):
 """Update layer mode description label and unit widgets. .. note:: This is an automatic Qt slot executed when the subcategory selection changes. """

        self.clear_further_steps()
        # Set widgets
        layer_mode = self.selected_layermode()
        # Exit if no selection
        if not layer_mode:
            self.lblDescribeLayerMode.setText('')
            return
        # Set description label
        self.lblDescribeLayerMode.setText(layer_mode['description'])
        # Enable the next button
        self.parent.pbnNext.setEnabled(True)