def METHOD_NAME(self, widget, event):
    if event.button == 1 and self.settings["on-left-click"]:
        self.launch(self.settings["on-left-click"])
    elif event.button == 2 and self.settings["on-middle-click"]:
        self.launch(self.settings["on-middle-click"])
    elif event.button == 3 and self.settings["on-right-click"]:
        self.launch(self.settings["on-right-click"])