public Builder clearModel() {
      model_ = getDefaultInstance().getModel();
      bitField0_ = (bitField0_ & ~0x00000004);
      onChanged();
      return this;
    }
<pre>
Optional. Which model to use for recognition requests. Select the model
best suited to your domain to get best results.

Guidance for choosing which model to use can be found in the [Transcription
Models
Documentation](https://cloud.google.com/speech-to-text/v2/docs/transcription-model)
and the models supported in each region can be found in the [Table Of
Supported
Models](https://cloud.google.com/speech-to-text/v2/docs/speech-to-text-supported-languages).
</pre>

<code>string model = 9 [(.google.api.field_behavior) = OPTIONAL];</code>

@return This builder for chaining.
java-speech/proto-google-cloud-speech-v2/src/main/java/com/google/cloud/speech/v2/RecognitionConfig.java