expanded_key

# File activesupport/lib/active_support/cache.rb, line 486
        def expanded_key(key) # :nodoc:
          return key.cache_key.to_s if key.respond_to?(:cache_key)

          case key
          when Array
            if key.size > 1
              key = key.collect{|element| expanded_key(element)}
            else
              key = key.first
            end
          when Hash
            key = key.sort_by { |k,_| k.to_s }.collect{|k,v| "#{k}=#{v}"}
          end

          key.to_param
        end