缺少的是签名

# Saving
builder = tf.saved_model.builder.SavedModelBuilder(export_dir)
builder.add_meta_graph_and_variables(sess, ["tag"], signature_def_map= {
        "model": tf.saved_model.signature_def_utils.predict_signature_def(
            inputs= {"x": x},
            outputs= {"finalnode": model})
        })
builder.save()

# loading
with tf.Session(graph=tf.Graph()) as sess:
    tf.saved_model.loader.load(sess, ["tag"], export_dir)
    graph = tf.get_default_graph()
    x = graph.get_tensor_by_name("x:0")
    model = graph.get_tensor_by_name("finalnode:0")
    print(sess.run(model, {x: [5, 6, 7, 8]}))