'Stop network.'

def stop(self):

    if (self.net is not None):
        for widget in self.widgetToItem:
            name = widget['text']
            tags = self.canvas.gettags(self.widgetToItem[widget])
            if ('Host' in tags):
                newHost = self.net.get(name)
                opts = self.hostOpts[name]
                if ('stopCommand' in opts):
                    newHost.cmdPrint(opts['stopCommand'])
            if ('Switch' in tags):
                newNode = self.net.get(name)
                opts = self.switchOpts[name]
                if ('stopCommand' in opts):
                    newNode.cmdPrint(opts['stopCommand'])
        self.net.stop()
    cleanUpScreens()
    self.net = None
