title: Typescript and Extending kendo DataSource
body: <p>I'm using KendoUI and typescript in my application and i want convert this code to typescript:</p>
  
  <pre><code>var customDataSource= kendo.data.DataSource.extend({
  
      init: function (options) {
  
          kendo.data.DataSource.fn.init.call(this, options);
     }
  });
  </code></pre>
  
  <p>But typescript can't convert and display error in this line:</p>
  
  <pre><code> kendo.data.DataSource.fn.init.call(this, options);
  </code></pre>
  
  <p>what is wrong?(I'm using kendo.all.d.ts)</p>