public Builder setGcsSource(com.google.cloud.translate.v3beta1.GcsSource value) {
      if (gcsSourceBuilder_ == null) {
        if (value == null) {
          throw new NullPointerException();
        }
        source_ = value;
        onChanged();
      } else {
        gcsSourceBuilder_.setMessage(value);
      }
      sourceCase_ = 2;
      return this;
    }
<pre>
Google Cloud Storage location. This must be a single file.
For example: gs://example_bucket/example_file.pdf
</pre>

<code>.google.cloud.translation.v3beta1.GcsSource gcs_source = 2;</code>
java-translate/proto-google-cloud-translate-v3beta1/src/main/java/com/google/cloud/translate/v3beta1/DocumentInputConfig.java