public Builder mergeCustomPronunciations(
        com.google.cloud.texttospeech.v1.CustomPronunciations value) {
      if (customPronunciationsBuilder_ == null) {
        if (((bitField0_ & 0x00000004) != 0)
            && customPronunciations_ != null
            && customPronunciations_
                != com.google.cloud.texttospeech.v1.CustomPronunciations.getDefaultInstance()) {
          getCustomPronunciationsBuilder().mergeFrom(value);
        } else {
          customPronunciations_ = value;
        }
      } else {
        customPronunciationsBuilder_.mergeFrom(value);
      }
      if (customPronunciations_ != null) {
        bitField0_ |= 0x00000004;
        onChanged();
      }
      return this;
    }
<pre>
Optional. The pronunciation customizations are applied to the input. If
this is set, the input is synthesized using the given pronunciation
customizations.

The initial support is for en-us, with plans to expand to other locales in
the future. Instant Clone voices aren't supported.

In order to customize the pronunciation of a phrase, there must be an exact
match of the phrase in the input types. If using SSML, the phrase must not
be inside a phoneme tag.
</pre>

<code>
.google.cloud.texttospeech.v1.CustomPronunciations custom_pronunciations = 5 [(.google.api.field_behavior) = OPTIONAL];
</code>
java-texttospeech/proto-google-cloud-texttospeech-v1/src/main/java/com/google/cloud/texttospeech/v1/StreamingSynthesizeConfig.java