old_contents: examples = [
      'dba1.mysql.*\.select group by 3',
      'thorin.beansdb group by 4',
      'thorin.doubanmemcache.*11211 group by 3',
      'thorin.doubanmemcache.*11212 group by 3',
      'thorin.doubanmemcache.*11213 group by 3',
      'thorin.doubanmemcache.*11214 group by 3',
      'thorin.beansmq group by 3'
  ]
  
new_contents: examples = [
      'dba1.mysql.*\.select group by 3',
      'thorin.beansdb group by 4',
      'thorin.doubanmemcache.*11211 group by 3',
      'thorin.doubanmemcache.*11212 group by 3',
      'thorin.doubanmemcache.*11213 group by 3',
      'thorin.doubanmemcache.*11214 group by 3',
      'thorin.beansmq group by 3',
      'thorin.iostat group by 3',
  ]
  
subject: add iostat