@java.lang.Override
    public com.google.protobuf.ByteString getMetadataFilterBytes() {
      java.lang.Object ref = metadataFilter_;
      if (ref instanceof java.lang.String) {
        com.google.protobuf.ByteString b =
            com.google.protobuf.ByteString.copyFromUtf8((java.lang.String) ref);
        metadataFilter_ = b;
        return b;
      } else {
        return (com.google.protobuf.ByteString) ref;
      }
    }
<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