def [](cache)
      c = cache.to_sym

      fail Exceptions::CacheDoesNotExist, "Unknown cache \":#{c}\" given. Did you create it in advance?"  unless caches.key?(c)
      caches[c]
    end
def [](cache)
      c = cache.to_sym

      fail Exceptions::CacheDoesNotExist, "Unknown cache \":#{c}\" given. Did you create it in advance?"  unless caches.key?(c)
      caches[c]
    end
Retrieve cache

 @param [Symbol] cache
   the cache to be used