code: private ClassName stackClassName(int stackDepth, String simpleName) {
      ClassName className = ClassName.get(packageName, typeSpecStack.get(0).name);
      for (int i = 1; i <= stackDepth; i++) {
        className = className.nestedClass(typeSpecStack.get(i).name);
      }
      return className.nestedClass(simpleName);
    }
docs: Returns the class named {@code simpleName} when nested in the class at {@code stackDepth}.