code: @Override
      public String getDescription() {
          StringBuilder sb = new StringBuilder();
          sb.append("Recursive datastructure.\nAdd prefab values for one of the following types: ");
          Iterator<TypeTag> i = typeStack.iterator();
          sb.append(i.next().toString());
          while(i.hasNext()) {
              sb.append(", ");
              sb.append(i.next().toString());
          }
          sb.append(".");
          return sb.toString();
      }
docs: {@inheritDoc}