code: def get_service_account_email(self, project=None):
          
          if project is None:
              project = self.project
          path = "/projects/%s/serviceAccount" % (project,)
          api_response = self._base_connection.api_request(method="GET", path=path)
          return api_response["email_address"]
docs: Get the email address of the project's GCS service account
  
          :type project: str
          :param project:
              (Optional) Project ID to use for retreiving GCS service account
              email address.  Defaults to the client's project.
  
          :rtype: str
          :returns: service account email address