old_contents: import Model from 'ember-data/model';
  import {belongsTo} from 'ember-data/relationships';
  import attr from 'ember-data/attr';
  
  export default Model.extend({
  
    playlist: belongsTo('playlist'),
    artist: attr('string'),
    album: attr('string'),
    title: attr('string'),
    duration: attr('string'),
    
    local: attr('boolean'),
    australian: attr('boolean'),
    female: attr('boolean'),
    newRelease: attr('boolean'),
  });
  
new_contents: import Model from 'ember-data/model';
  import {belongsTo} from 'ember-data/relationships';
  import attr from 'ember-data/attr';
  
  export default Model.extend({
  
    playlist: belongsTo('playlist'),
  
    index: attr('number'),
  
    artist: attr('string'),
    album: attr('string'),
    title: attr('string'),
    duration: attr('string'),
    
    local: attr('boolean'),
    australian: attr('boolean'),
    female: attr('boolean'),
    newRelease: attr('boolean'),
  });
  
subject: Add index to Ember's PlaylistEntry model.