title: How to define empty dict<string, int> in hacklang
body: <p>I have following shape:</p>
  
  <pre><code>const type A = shape(
    'b' =&gt; dict&lt;string, int&gt;,
  );
  </code></pre>
  
  <p>How do I create this shape with empty dict? For example from this function</p>
  
  <pre><code>function getA(): A {
    return shape(
      'b' =&gt; ???
    );
  }
  </code></pre>