private com.google.protobuf.SingleFieldBuilderV3<
            com.google.cloud.vertexai.api.RagRetrievalConfig.Filter,
            com.google.cloud.vertexai.api.RagRetrievalConfig.Filter.Builder,
            com.google.cloud.vertexai.api.RagRetrievalConfig.FilterOrBuilder>
        getFilterFieldBuilder() {
      if (filterBuilder_ == null) {
        filterBuilder_ =
            new com.google.protobuf.SingleFieldBuilderV3<
                com.google.cloud.vertexai.api.RagRetrievalConfig.Filter,
                com.google.cloud.vertexai.api.RagRetrievalConfig.Filter.Builder,
                com.google.cloud.vertexai.api.RagRetrievalConfig.FilterOrBuilder>(
                getFilter(), getParentForChildren(), isClean());
        filter_ = null;
      }
      return filterBuilder_;
    }
<pre>
Optional. Config for filters.
</pre>

<code>
.google.cloud.vertexai.v1.RagRetrievalConfig.Filter filter = 3 [(.google.api.field_behavior) = OPTIONAL];
</code>
java-vertexai/proto-google-cloud-vertexai-v1/src/main/java/com/google/cloud/vertexai/api/RagRetrievalConfig.java