docs: public final TypeInfo innerClass(String simpleName) {
      checkArgument(
          simpleName.indexOf('$') == -1, "Simple names shouldn't contain '$': %s", simpleName);
      String className = className() + '$' + simpleName;
      String internalName = internalName() + '$' + simpleName;
      Type type = Type.getObjectType(internalName);
      return new AutoValue_TypeInfo(className, simpleName, internalName, type);
    }