code: public static <T extends IsSerializable> StorageKey<T> isSerializableKey(String keyName){
        return new StorageKey<>(keyName, IsSerializable.class);
    }
docs: Returns IsSerializable type value's storage key.
  
  @param keyName name of storage key
  @param <T> type of value
  @return IsSerializable type value's storage key