def fetch(key, cache_options, &block)
      if defined?(Rails)
        Rails.cache.fetch(key, cache_options, &block)
      else
        @cache[key] ||= yield
      end
    end
def fetch(key, cache_options, &block)
      if defined?(Rails)
        Rails.cache.fetch(key, cache_options, &block)
      else
        @cache[key] ||= yield
      end
    end
Fetch given a key and options and a fallback block attempts to find the key in the cache
 and stores the block result in there if no key is found.

 cache = Rabl::CacheEngine.new; cache.fetch("some_key") { "fallback data" }