How to use the sparkpost.__version__ function in sparkpost

def request(self, method, uri, **kwargs):
        headers = {
            'User-Agent': 'python-sparkpost/' + sparkpost.__version__,
            'Content-Type': 'application/json',
            'Authorization': self.api_key
        }
        response = self.transport.request(method, uri, headers=headers,
                                          **kwargs)
        return response