@java.lang.Override
  public com.google.protobuf.Struct getMetadata() {
    return metadata_ == null ? com.google.protobuf.Struct.getDefaultInstance() : metadata_;
  }
<pre>
Input only. This field is for users to attach user managed metadata.
</pre>

<code>.google.protobuf.Struct metadata = 3 [(.google.api.field_behavior) = INPUT_ONLY];</code>

@return The metadata.
java-visionai/proto-google-cloud-visionai-v1/src/main/java/com/google/cloud/visionai/v1/PacketHeader.java