def on_click(self, event):
button = event["<STR_LIT>"]<EOL>if button == self.button_up:<EOL><INDENT>self.backend.volume_up(self.volume_delta)<EOL><DEDENT>elif button == self.button_down:<EOL><INDENT>self.backend.volume_down(self.volume_delta)<EOL><DEDENT>elif button == self.button_mute:<EOL><INDENT>self.backend.toggle_mute()<EOL><DEDENT>
Volume up/down and toggle mute.