public Builder clearSourceLanguageCode() {
        sourceLanguageCode_ = getDefaultInstance().getSourceLanguageCode();
        bitField0_ = (bitField0_ & ~0x00000001);
        onChanged();
        return this;
      }
<pre>
Required. The ISO-639 language code of the input text, for example,
"en-US". Expected to be an exact match for GlossaryTerm.language_code.
</pre>

<code>string source_language_code = 1;</code>

@return This builder for chaining.
java-translate/proto-google-cloud-translate-v3/src/main/java/com/google/cloud/translate/v3/Glossary.java