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     ### Headers
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     ### 请求头(Headers)
   
     The `Content-Type` header allows us to inform the server that the body will represent JSON.
  
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    ### JSON results
    ### JSON结果
  
    As with `getHeroes()`, we [extract the data](#extract-data) from the response using the
  
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      # RxJS Library
  
      # RxJS库
  
      [RxJS](https://github.com/ReactiveX/RxJS) ("Reactive Extensions") is a 3rd party library, endorsed by Angular,
      that implements the [*asynchronous observable*](https://www.youtube.com/watch?v=UHI0AzD_WfY "Rob Wormald on observables") pattern.
      
  