private com.google.protobuf.SingleFieldBuilderV3<
            com.google.protobuf.Timestamp,
            com.google.protobuf.Timestamp.Builder,
            com.google.protobuf.TimestampOrBuilder>
        getIndexTimeFieldBuilder() {
      if (indexTimeBuilder_ == null) {
        indexTimeBuilder_ =
            new com.google.protobuf.SingleFieldBuilderV3<
                com.google.protobuf.Timestamp,
                com.google.protobuf.Timestamp.Builder,
                com.google.protobuf.TimestampOrBuilder>(
                getIndexTime(), getParentForChildren(), isClean());
        indexTime_ = null;
      }
      return indexTimeBuilder_;
    }
<pre>
Output only. The time at which this ProductSet was last indexed. Query
results will reflect all updates before this time. If this ProductSet has
never been indexed, this timestamp is the default value
"1970-01-01T00:00:00Z".

This field is ignored when creating a ProductSet.
</pre>

<code>.google.protobuf.Timestamp index_time = 3 [(.google.api.field_behavior) = OUTPUT_ONLY];
</code>
java-vision/proto-google-cloud-vision-v1/src/main/java/com/google/cloud/vision/v1/ProductSet.java