public Builder setAuthor(java.lang.String value) {
   if (value == null) {
     throw new NullPointerException();
   }
   result.hasAuthor = true;
   result.author_ = value;
   return this;
 }
 public Builder clearAuthor() {
   result.hasAuthor = false;
   result.author_ = getDefaultInstance().getAuthor();
   return this;
 }