title: How to assign namespaces to an property of classes in typescript
body: <p>I'm adding a declaration file to a package for typescript。
  There are some syntax like this:</p>
  
  <pre><code>const Sequelize = require('Sequelize');
  //...
  class Application {
      Sequelize = Sequelize;
  }
  </code></pre>
  
  <p>So I wrote a file（index.d.ts）like this:</p>
  
  <pre><code>import * as Sequelize from 'sequelize'; // this @types/sequelize export a namespace
  //...
  interface Application{
      Sequelize: Sequelize; // &lt;---error TS2709: Cannot use namespace 'Sequelize' as a type.
  }
  </code></pre>
  
  <p>How do I solve this problem?</p>