private com.google.protobuf.RepeatedFieldBuilderV3<
            com.google.cloud.speech.v1.CustomClass,
            com.google.cloud.speech.v1.CustomClass.Builder,
            com.google.cloud.speech.v1.CustomClassOrBuilder>
        getCustomClassesFieldBuilder() {
      if (customClassesBuilder_ == null) {
        customClassesBuilder_ =
            new com.google.protobuf.RepeatedFieldBuilderV3<
                com.google.cloud.speech.v1.CustomClass,
                com.google.cloud.speech.v1.CustomClass.Builder,
                com.google.cloud.speech.v1.CustomClassOrBuilder>(
                customClasses_,
                ((bitField0_ & 0x00000004) != 0),
                getParentForChildren(),
                isClean());
        customClasses_ = null;
      }
      return customClassesBuilder_;
    }
<pre>
A collection of custom classes. To specify the classes inline, leave the
class' `name` blank and fill in the rest of its fields, giving it a unique
`custom_class_id`. Refer to the inline defined class in phrase hints by its
`custom_class_id`.
</pre>

<code>repeated .google.cloud.speech.v1.CustomClass custom_classes = 3;</code>
java-speech/proto-google-cloud-speech-v1/src/main/java/com/google/cloud/speech/v1/SpeechAdaptation.java