anchor.diff:    ### The safe navigation operator ( ?. ) and null property paths
   
     The Angular **safe navigation operator (`?.`)** is a fluent and convenient way to guard against null and undefined values in property paths.
  -  Here it is, protecting against a view render failure if the `currentHero` is null.
  +  Here it is used to protect against against a view render failure if the `currentHero` is null:
   +makeExample('template-syntax/ts/app/app.component.html', 'safe-2')(format=".")
   
   block dart-safe-nav-op
  
positive.code:     The `json` pipe is particularly helpful for debugging our bindings:
    +makeExample('template-syntax/ts/app/app.component.html', 'pipes-json')(format=".")
    :marked
      The generated output would look something like this
    code-example(language="json").
      { "firstName": "Hercules", "lastName": "Son of Zeus",
        "birthdate": "1970-02-25T08:00:00.000Z",
  
negative.code:   We can chain expressions through multiple pipes:
  +makeExample('template-syntax/ts/app/app.component.html', 'pipes-2')(format=".")
  :marked
    We can also [apply parameters](./pipes.html#parameterizing-a-pipe) to a pipe:
  +makeExample('template-syntax/ts/app/app.component.html', 'pipes-3')(format=".")
  
  block json-pipe
  