title: python3 nested dictionary unpack for format string
body: <p>I am trying to pass a dictionary (loaded from JSON file) to format string. While single key-value <strong>unpack</strong> works correctly, I am not sure how I can access the <strong>nested keys</strong> (children) with a format string.</p>
  <p>Or is there any other better way to pass JSON to string format?</p>
  <pre><code>config = {
      &quot;TEST&quot;: &quot;TEST&quot;,
      &quot;TEST1&quot;: &quot;TEST1&quot;,
      &quot;TEST2&quot;: {
          &quot;TEST21&quot;: &quot;TEST21&quot;
      }
  }
  
  query_1 = &quot;&quot;&quot;
      {TEST} {TEST1}
  &quot;&quot;&quot;
  query_2 = &quot;&quot;&quot;
      {TEST} {TEST1}
      {TEST2.TEST21}
  &quot;&quot;&quot;
  
  print(query_1.format( **config ))  # WORKING
  print(query_2.format( **config ))  # NOT WORKING
  </code></pre>