How to use the slackclient.version.__version__ function in slackclient

def test_custom_user_agent(mocker):
    requests = mocker.patch('slackclient.slackrequest.requests')
    request = SlackRequest()

    request.append_user_agent("fooagent1", "0.1")
    request.append_user_agent("baragent/2", "0.2")

    request.do('xoxb-123', 'chat.postMessage', {'text': 'test', 'channel': '#general'})
    args, kwargs = requests.post.call_args

    # Verify user-agent includes both default and custom agent info
    assert "slackclient/{}".format(__version__) in kwargs['headers']['user-agent']
    assert "fooagent1/0.1" in kwargs['headers']['user-agent']

    # verify escaping of slashes in custom agent name
    assert "baragent:2/0.2" in kwargs['headers']['user-agent']

def __init__(
            self,
            proxies=None
    ):
        # HTTP configs
        self.custom_user_agent = None
        self.proxies = proxies

        # Construct the user-agent header with the package info, Python version and OS version.
        self.default_user_agent = {
            # __name__ returns all classes, we only want the client
            "client": "{0}/{1}".format(__name__.split('.')[0], __version__),
            "python": "Python/{v.major}.{v.minor}.{v.micro}".format(v=sys.version_info),
            "system": "{0}/{1}".format(platform.system(), platform.release())
        }