code: public com.google.cloud.datalabeling.v1beta1.GcsSource getGcsSource() {
      if (sourceCase_ == 2) {
        return (com.google.cloud.datalabeling.v1beta1.GcsSource) source_;
      }
      return com.google.cloud.datalabeling.v1beta1.GcsSource.getDefaultInstance();
    }
docs: <code>.google.cloud.datalabeling.v1beta1.GcsSource gcs_source = 2;</code>