private com.google.protobuf.SingleFieldBuilderV3<
            com.google.cloud.vertexai.api.GenerationConfig.RoutingConfig,
            com.google.cloud.vertexai.api.GenerationConfig.RoutingConfig.Builder,
            com.google.cloud.vertexai.api.GenerationConfig.RoutingConfigOrBuilder>
        getRoutingConfigFieldBuilder() {
      if (routingConfigBuilder_ == null) {
        routingConfigBuilder_ =
            new com.google.protobuf.SingleFieldBuilderV3<
                com.google.cloud.vertexai.api.GenerationConfig.RoutingConfig,
                com.google.cloud.vertexai.api.GenerationConfig.RoutingConfig.Builder,
                com.google.cloud.vertexai.api.GenerationConfig.RoutingConfigOrBuilder>(
                getRoutingConfig(), getParentForChildren(), isClean());
        routingConfig_ = null;
      }
      return routingConfigBuilder_;
    }
<pre>
Optional. Routing configuration.
</pre>

<code>
optional .google.cloud.vertexai.v1.GenerationConfig.RoutingConfig routing_config = 17 [(.google.api.field_behavior) = OPTIONAL];
</code>
java-vertexai/proto-google-cloud-vertexai-v1/src/main/java/com/google/cloud/vertexai/api/GenerationConfig.java