code: def testLocalLeader(self):
      cluster_spec = {}
      self.assertEqual(
          multi_worker_util.collective_leader(cluster_spec, None, 0), ""
      )
  
imports: from tensorflow.core.protobuf import cluster_pb2
  from tensorflow.python.distribute import multi_worker_util
  from tensorflow.python.eager import test
  from tensorflow.python.training import server_lib
label_desc: Use image node_id 4 for calling the CollectiveLeaderTest obj's underlying member method code with example usage: obj.testLocalLeader() without return types