<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def unschedule(self):
 """ Given a a list of scheduled functions, tear down their regular execution. """


        # Run even if events are not defined to remove previously existing ones (thus default to []).
        events = self.stage_config.get('events', [])

        if not isinstance(events, list): # pragma: no cover
            print("Events must be supplied as a list.")
            return

        function_arn = None
        try:
            function_response = self.zappa.lambda_client.get_function(FunctionName=self.lambda_name)
            function_arn = function_response['Configuration']['FunctionArn']
        except botocore.exceptions.ClientError as e: # pragma: no cover
            raise ClickException("Function does not exist, you should deploy first. Ex: zappa deploy {}. "
                  "Proceeding to unschedule CloudWatch based events.".format(self.api_stage))

        print("Unscheduling..")
        self.zappa.unschedule_events(
            lambda_name=self.lambda_name,
            lambda_arn=function_arn,
            events=events,
            )

        # Remove async task SNS
        if self.stage_config.get('async_source', None) == 'sns' \
           and self.stage_config.get('async_resources', True):
            removed_arns = self.zappa.remove_async_sns_topic(self.lambda_name)
            click.echo('SNS Topic removed: %s' % ', '.join(removed_arns))