anchor.diff:      We're importing some extra symbols from the Angular core library that we're not using yet.
       They'll become relevant later in this page.
     
  -    我们正在从Angular核心库中导入一些从未用过的符号，稍后我们会接触它们。
  +    我们正在从Angular核心库中导入一些从未用到的符号，稍后我们会接触它们。
   
   :marked
     The `@NgModule` metadata should be familiar. 
  
positive.code:   :marked
      The real problem is that there are _two different classes_ trying to do the same thing.
      
      真正的问题在于，有_两个不同的类_视图做同一件事。
  
      It's OK to import the _same_ directive class multiple times. 
      Angular removes duplicate classes and only registers one of them.
  
negative.code: 
    * The root `AppModule` grows larger with each new application class and shows no signs of stopping.
    
    * 随着一个个类被加入应用中，根模块`AppModule`变大了，并且还会继续变大。
  
    * We have conflicting directives. 
    
  