@Override
 public WritableScope changeLockLevel(LockLevel lockLevel) {
   if (lockLevel.ordinal() < this.lockLevel.ordinal()) {
     throw new IllegalStateException(
         "cannot lower lock level from "
             + this.lockLevel
             + " to "
             + lockLevel
             + " at "
             + debugName);
   }
   this.lockLevel = lockLevel;
   return this;
 }