code: def testOverlappingSparseJobMergedClusterResolverThrowError(self):
      cluster_spec_1 = server_lib.ClusterSpec(
          {"worker": {7: "worker4:2222", 9: "worker5:2222"}}
      )
      cluster_spec_2 = server_lib.ClusterSpec(
          {
              "worker": {
                  3: "worker0:2222",
                  6: "worker1:2222",
                  7: "worker2:2222",
              }
          }
      )
      cluster_resolver_1 = cluster_resolver.SimpleClusterResolver(
          cluster_spec_1
      )
      cluster_resolver_2 = cluster_resolver.SimpleClusterResolver(
          cluster_spec_2
      )
  
      union_cluster = cluster_resolver.UnionClusterResolver(
          cluster_resolver_1, cluster_resolver_2
      )
      self.assertRaises(KeyError, union_cluster.cluster_spec)
  
imports: from tensorflow.python.client import session
  from tensorflow.python.distribute.cluster_resolver import 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 12 for calling the UnionClusterResolverTest obj's underlying member method code with example usage: obj.testOverlappingSparseJobMergedClusterResolverThrowError() without return types