#AMD Template
   Use the template below when starting to define a new class.
   
   ``` js
   define(['altair/facades/declare',
           'altair/mixins/_DeferredMixin',
           'altair/mixins/_AssertMixin'
   ], function (declare,
                _DeferredMixin,
                _AssertMixin) {
   
       return declare([_DeferredMixin, _AssertMixin], {
   
   
       });
   
   });
   ```