private com.google.protobuf.SingleFieldBuilderV3<
            com.google.cloud.visionai.v1.SeriesMetadata,
            com.google.cloud.visionai.v1.SeriesMetadata.Builder,
            com.google.cloud.visionai.v1.SeriesMetadataOrBuilder>
        getSeriesMetadataFieldBuilder() {
      if (seriesMetadataBuilder_ == null) {
        seriesMetadataBuilder_ =
            new com.google.protobuf.SingleFieldBuilderV3<
                com.google.cloud.visionai.v1.SeriesMetadata,
                com.google.cloud.visionai.v1.SeriesMetadata.Builder,
                com.google.cloud.visionai.v1.SeriesMetadataOrBuilder>(
                getSeriesMetadata(), getParentForChildren(), isClean());
        seriesMetadata_ = null;
      }
      return seriesMetadataBuilder_;
    }
<pre>
Input only. Immutable. Metadata that the server needs to know where to
write the packets to. It's only required for the first packet.
</pre>

<code>
.google.cloud.visionai.v1.SeriesMetadata series_metadata = 5 [(.google.api.field_behavior) = INPUT_ONLY, (.google.api.field_behavior) = IMMUTABLE];
</code>
java-visionai/proto-google-cloud-visionai-v1/src/main/java/com/google/cloud/visionai/v1/PacketHeader.java