public Builder mergeRetrievalMetadata(com.google.cloud.vertexai.api.RetrievalMetadata value) {
      if (retrievalMetadataBuilder_ == null) {
        if (((bitField0_ & 0x00000010) != 0)
            && retrievalMetadata_ != null
            && retrievalMetadata_
                != com.google.cloud.vertexai.api.RetrievalMetadata.getDefaultInstance()) {
          getRetrievalMetadataBuilder().mergeFrom(value);
        } else {
          retrievalMetadata_ = value;
        }
      } else {
        retrievalMetadataBuilder_.mergeFrom(value);
      }
      if (retrievalMetadata_ != null) {
        bitField0_ |= 0x00000010;
        onChanged();
      }
      return this;
    }
<pre>
Optional. Output only. Retrieval metadata.
</pre>

<code>
optional .google.cloud.vertexai.v1.RetrievalMetadata retrieval_metadata = 7 [(.google.api.field_behavior) = OPTIONAL, (.google.api.field_behavior) = OUTPUT_ONLY];
</code>
java-vertexai/proto-google-cloud-vertexai-v1/src/main/java/com/google/cloud/vertexai/api/GroundingMetadata.java