message: show teacher hint
diff: [theme]="'github'"
  [readOnly]="true">
  </ace-editor>
  - <div>Your code goes here:</div>
  + <div *ngIf="!isExampleCode">Your code goes here:</div>
  + <div *ngIf="isExampleCode">This is the provided example solution:</div>
  <ace-editor class="user-code-editor"
  #codeEditor
  [(text)]="codeKata.code || progress.code"
  