anchor.diff:      The `import 'rxjs/add/...'` syntax may be unfamiliar.
       It's missing the usual list of symbols between the braces: `{...}`.
   
  -    你可能并不熟悉`import 'rxjs/add/...'`语法，缺少了括号之间的导入列表：`{...}`。
  +    你可能并不熟悉这种`import 'rxjs/add/...'`语法，它缺少了花括号中的导入列表：`{...}`。
       
       We don't need the operator symbols themselves. 
       In each case, the mere act of importing the library
       loads and executes the library's script file which, in turn, adds the operator to the `Observable` class.
   
  -    其实我们并不需要操作符本身，正常情况下，导入库不过是加载和执行库所对应的脚本文件，
  -    然后依次将操作符作为方法添加到`Observable`类中。
  +    这是因为我们并不需要操作符本身，这种情况下，我们所做的其实是导入这个库，加载并运行其中的脚本，
  +    它会把操作符添加到`Observable`类中。
   
   :marked
     ### Add the search component to the dashboard
  
positive.code:     after chaining it to another RxJS operator, <code>map</code>, 
      to extract heroes from the response data.
  
      更重要的不同：我们不再调用`toPromise`方法，而是从`http.get`
      方法中返回一个*Observable*对象，之后链式调用RxJS操作<code>map</code>
      来从返回数据中提取英雄。
  
      RxJS operator chaining makes response processing easy and readable.
  
negative.code:   We still return a !{_Promise} from both methods. 
    We won't have to update any of the components that call them.
  
    尽管我们在`getHeroes()`和`getHero()`方法的*内部*做了重大修改，
    但是他们的公共签名却没有变。这两个方法仍然返回的是一个!{Promise}对象，
    所以并不需要修改任何调用他们的组件。
  
    Our stakeholders are thrilled with the web API integration so far.
    Now they want the ability to create and delete heroes.
  