@java.lang.Override
    public Builder newBuilderForType() {
      return newBuilder();
    }
<pre>
Optional. String for metadata filtering.
</pre>

<code>string metadata_filter = 2 [(.google.api.field_behavior) = OPTIONAL];</code>

@return The bytes for metadataFilter.
java-vertexai/proto-google-cloud-vertexai-v1/src/main/java/com/google/cloud/vertexai/api/RagRetrievalConfig.java