module ActiveModel::Serializer::Caching

def cache_key(adapter_instance)
  return @cache_key if defined?(@cache_key)
  parts = []
  parts << object_cache_key
  parts << adapter_instance.cache_key
  parts << serializer_class._cache_digest unless serializer_class._skip_digest?
  @cache_key = expand_cache_key(parts)
end