anchor.diff:  :marked
     ### Hero service _delete()_ method
     
  -  ### hero 服务的`delete`方法
  +  ### hero 服务的`delete()`方法
   
     Add the hero service's `delete()` method, which uses the `delete()` HTTP method to remove the hero from the server:
   
  
positive.code:   This demo service logs the error to the console; in real life,
    you would handle the error in code. For a demo, this works.
    
    在这个范例服务中，我们把错误记录到控制台中；在真实世界中，我们应该做得更好。
  
    The code also includes an error to
    the caller in a rejected promise, so that the caller can display a proper error message to the user.
  
negative.code:     doesn't actually abort a pending HTTP request.
      For now , unwanted resultsare discarded.
      
      注意，*取消*`HeroSearchService`的可观察对象并不会实际中止 (abort) 一个未完成的 HTTP 请求，
      除非服务支持这个特性，这个问题我们以后再讨论。
      目前我们的做法只是丢弃不希望的结果。
      
  