public Builder clearModelName() {
          modelName_ = getDefaultInstance().getModelName();
          bitField0_ = (bitField0_ & ~0x00000001);
          onChanged();
          return this;
        }
<pre>
Optional. The model name of the rank service.
Format: `semantic-ranker-512&#64;latest`
</pre>

<code>optional string model_name = 1 [(.google.api.field_behavior) = OPTIONAL];</code>

@return This builder for chaining.
java-vertexai/proto-google-cloud-vertexai-v1/src/main/java/com/google/cloud/vertexai/api/RagRetrievalConfig.java