private void ensureCustomClassesIsMutable() {
      if (!((bitField0_ & 0x00000004) != 0)) {
        customClasses_ =
            new java.util.ArrayList<com.google.cloud.speech.v1p1beta1.CustomClass>(customClasses_);
        bitField0_ |= 0x00000004;
      }
    }
<pre>
A collection of phrase set resource names to use.
</pre>

<code>repeated string phrase_set_references = 2 [(.google.api.resource_reference) = { ... }
</code>

@param value The bytes of the phraseSetReferences to add.
@return This builder for chaining.
java-speech/proto-google-cloud-speech-v1p1beta1/src/main/java/com/google/cloud/speech/v1p1beta1/SpeechAdaptation.java