@java.lang.Override
    public void writeTo(com.google.protobuf.CodedOutputStream output) throws java.io.IOException {
      if (boxId_ != 0L) {
        output.writeInt64(1, boxId_);
      }
      if (((bitField0_ & 0x00000001) != 0)) {
        output.writeMessage(2, getNormalizedBoundingBox());
      }
      if (java.lang.Float.floatToRawIntBits(score_) != 0) {
        output.writeFloat(3, score_);
      }
      if (((bitField0_ & 0x00000002) != 0)) {
        output.writeMessage(4, getEntity());
      }
      if (trackId_ != 0L) {
        output.writeInt64(5, trackId_);
      }
      getUnknownFields().writeTo(output);
    }
<pre>
An unique id to identify a track. It should be consistent across frames.
It only exists if tracking is enabled.
</pre>

<code>int64 track_id = 5;</code>

@return The trackId.
java-visionai/proto-google-cloud-visionai-v1/src/main/java/com/google/cloud/visionai/v1/OccupancyCountingPredictionResult.java