private com.google.protobuf.SingleFieldBuilderV3<
            com.google.cloud.visionai.v1.AssetSource,
            com.google.cloud.visionai.v1.AssetSource.Builder,
            com.google.cloud.visionai.v1.AssetSourceOrBuilder>
        getAssetSourceFieldBuilder() {
      if (assetSourceBuilder_ == null) {
        assetSourceBuilder_ =
            new com.google.protobuf.SingleFieldBuilderV3<
                com.google.cloud.visionai.v1.AssetSource,
                com.google.cloud.visionai.v1.AssetSource.Builder,
                com.google.cloud.visionai.v1.AssetSourceOrBuilder>(
                getAssetSource(), getParentForChildren(), isClean());
        assetSource_ = null;
      }
      return assetSourceBuilder_;
    }
<pre>
The source of the asset.
</pre>

<code>.google.cloud.visionai.v1.AssetSource asset_source = 2;</code>
java-visionai/proto-google-cloud-visionai-v1/src/main/java/com/google/cloud/visionai/v1/UploadAssetRequest.java