in flink-connector-opensearch/src/main/java/org/apache/flink/connector/opensearch/sink/OpensearchSinkBuilder.java [94:104]
public <T extends IN> OpensearchSinkBuilder<T> setEmitter(
OpensearchEmitter<? super T> emitter) {
checkNotNull(emitter);
checkState(
InstantiationUtil.isSerializable(emitter),
"The Opensearch emitter must be serializable.");
final OpensearchSinkBuilder<T> self = self();
self.emitter = emitter;
return self;
}