code: def _build_session(self, auth_class, *args, **kwargs):
          
          session = requests.session()
          session.auth = auth_class(*args, **kwargs)
          session.headers.update({'CB-VERSION': self.API_VERSION,
                                  'Accept': 'application/json',
                                  'Content-Type': 'application/json',
                                  'User-Agent': 'coinbase/python/2.0'})
          return session
docs: Internal helper for creating a requests `session` with the correct
          authentication handling.