如何打印可读性强的json：(pretty Readablejsoninruby)

http://stackoverflow.com/questions/86653/how-can-i-pretty-format-my-json-output-in-ruby-on-rails

 43     json = Cms::Utils.object(videoid)
 44     logger.info "== json for url( #{url}) : #{JSON.pretty_generate(json)}"