code: public com.google.protobuf.ByteString
        getExtendsBytes() {
      java.lang.Object ref = extends_;
      if (ref instanceof java.lang.String) {
        com.google.protobuf.ByteString b = 
            com.google.protobuf.ByteString.copyFromUtf8(
                (java.lang.String) ref);
        extends_ = b;
        return b;
      } else {
        return (com.google.protobuf.ByteString) ref;
      }
    }
docs: <pre>
  Allows extending whitelists of rules with the specified rule_id. If this
  field is specified then all fields except whitelist, whitelist_regexp,
  only_apply_to and only_apply_to_regexp are ignored.
  </pre>
  
  <code>optional string extends = 10;</code>