How to use the gokart.slack function in gokart

def test_send(self, patch):
        def _api_call(*args, **kwargs):
            if args[0] == 'channels.list':
                return {'ok': True, 'channels': [{'name': 'valid', 'id': 'valid_id'}], 'response_metadata': {'next_cursor': ''}}
            if args[0] == 'files.upload':
                return {'ok': True}
            assert False

        mock_client = MagicMock()
        mock_client.api_call = MagicMock(side_effect=_api_call)
        patch.return_value = mock_client

        api = gokart.slack.SlackAPI(token='valid', channel='valid', to_user='test user')
        api.send_snippet(comment='test', title='title', content='content')

def _try_get_slack_api(cmdline_args: List[str]) -> Optional[gokart.slack.SlackAPI]:
    with CmdlineParser.global_instance(cmdline_args):
        config = gokart.slack.SlackConfig()
        token = config.token_name
        channel = config.channel
        to_user = config.to_user
        if token and channel:
            logger.info('Slack notification is activated.')
            return gokart.slack.SlackAPI(token=token, channel=channel, to_user=to_user)
    logger.info('Slack notification is not activated.')
    return None

def _try_get_slack_api(cmdline_args: List[str]) -> Optional[gokart.slack.SlackAPI]:
    with CmdlineParser.global_instance(cmdline_args):
        config = gokart.slack.SlackConfig()
        token = config.token_name
        channel = config.channel
        to_user = config.to_user
        if token and channel:
            logger.info('Slack notification is activated.')
            return gokart.slack.SlackAPI(token=token, channel=channel, to_user=to_user)
    logger.info('Slack notification is not activated.')
    return None