title: Pop the first inserted key-value pair in a dictionary [Python 3.7+]
body: <p>Suppose I have a dictionary in <code>python 3.9</code>:</p>
  <pre class="lang-py prettyprint-override"><code>dictionary = {
      'a': 2,
      'b': 3,
      'c': 4
  }
  </code></pre>
  <p>If I use <code>dictionary.popitem()</code>, it pops and returns <code>('c', 4)</code>. <br>
  Is there any way to retrieve <code>('a', 2)</code>, i.e the first item, in <code>O(1)</code> time?</p>