anchor.diff:    The `!{_priv}http.get()` call in `HeroSearchService` is similar to the one
     in the `HeroService`, although the URL now has a query string.
   
  -  <span if-docs="ts">A more important difference: we no longer call `toPromise`.
  -  Instead we return the *observable* from the the `htttp.get`, 
  -  after chaining it to another RxJS operator, <code>map</code>, 
  -  to extract heroes from the response data.
  -
  -  RxJS operator chaining makes response processing easy and readable.
  -  See the [discuss below about operators](#rxjs-imports).
  -  </span>
  -
  ++ifDocsFor('ts')
  +  :marked
  +    A more important difference: we no longer call `toPromise`.
  +    Instead we return the *observable* from the the `htttp.get`, 
  +    after chaining it to another RxJS operator, <code>map</code>, 
  +    to extract heroes from the response data.
  +
  +    RxJS operator chaining makes response processing easy and readable.
  +    See the [discuss below about operators](#rxjs-imports).
  +
  +:marked
     ### HeroSearchComponent
   
     Let's create a new `HeroSearchComponent` that calls this new `HeroSearchService`.
  
positive.code:   It's easy with *!{_Observable}s* as we'll see.
  
    ### Search-by-name
    We're going to add a *hero search* feature to the Tour of Heroes.
    As the user types a name into a search box, we'll make repeated HTTP requests for heroes filtered by that name.
  
  
negative.code:   a#rxjs-imports
    :marked
      ### Import RxJS operators
  
      Most RxJS operators are not included in Angular's base `Observable` implementation.
      The base implementation includes only what Angular itself requires.
  
  