def add_version(self, project, version, egg):
        """
        Adds a new project egg to the Scrapyd service. First class, maps to
        Scrapyd's add version endpoint.
        """
        url = self._build_url(constants.ADD_VERSION_ENDPOINT)
        data = {
            'project': project,
            'version': version
        }
        files = {
            'egg': egg
        }
        json = self.client.post(url, data=data, files=files,
                                timeout=self.timeout)
        return json['spiders']
Adds a new project egg to the Scrapyd service. First class, maps to
        Scrapyd's add version endpoint.