code: def testZeroItemsInClusterSpecMasterRead(self):
      os.environ[
          "TF_CONFIG"
      ] = """
      {}
      """
  
      cluster_resolver = (
          tfconfig_cluster_resolver.TFConfigClusterResolver()
      )
      self.assertEqual("", cluster_resolver.master())
  
imports: import os
  from tensorflow.python.client import session
  from tensorflow.python.distribute.cluster_resolver import tfconfig_cluster_resolver
  from tensorflow.python.eager import context
  from tensorflow.python.framework import config
  from tensorflow.python.framework import test_util
  from tensorflow.python.platform import test
  from tensorflow.python.training import server_lib
label_desc: Use image node_id 13 for calling the TFConfigClusterResolverTest obj's underlying member method code with example usage: obj.testZeroItemsInClusterSpecMasterRead() without return types