private void ensureTargetLanguageCodesIsMutable() {
      if (!targetLanguageCodes_.isModifiable()) {
        targetLanguageCodes_ = new com.google.protobuf.LazyStringArrayList(targetLanguageCodes_);
      }
      bitField0_ |= 0x00000004;
    }
<pre>
Required. Source language code.
</pre>

<code>string source_language_code = 2 [(.google.api.field_behavior) = REQUIRED];</code>

@param value The bytes for sourceLanguageCode to set.
@return This builder for chaining.
java-translate/proto-google-cloud-translate-v3/src/main/java/com/google/cloud/translate/v3/BatchTranslateTextRequest.java