What is the tensorflow java API for tf.train.Example.SerializeToString in python?

Trying to convert some python tensorflow code to java, I can't find the same java API for train.example.SerializeToString in python. It is surely not java toString. I can find the java Example class here https://www.javadoc.io/doc/org.tensorflow/proto/latest/org/tensorflow/example/package-summary.html but there are simply no such API as SerializeToString.

in Python

features["a"] = tf.train.Feature(int64_list=tf.train.Int64List(value=list(values_a)))
features["b"] = tf.train.Feature(int64_list=tf.train.Int64List(value=list(values_b)))
tf_example = tf.train.Example(features=tf.train.Features(feature=features))
model_input = tf_example.SerializeToString()

I can convert to java

Feature featureA = Feature.newBuilder().setInt64List(value_a).build();
Feature featureB = Feature.newBuilder().setInt64List(value_b).build();
Map<String, Feature> featureNameAndValueMap = new HashMap<>();
featureNameAndValueMap.put("a", featureA);
featureNameAndValueMap.put("b", featureB);
Example example = Example.newBuilder().setFeatures(features).build();
//String modelInput = example.to???

Thanks a lot

Copyright License：
Author:「David chang」,Reproduced under the CC 4.0 BY-SA copyright license with link to original source & disclaimer.
Link to：https://stackoverflow.com/questions/63421332/what-is-the-tensorflow-java-api-for-tf-train-example-serializetostring-in-python