title: CSS class align-self-end not working
body: <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
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  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;link href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" rel="stylesheet" /&gt;
  &lt;div class="col-md-3"&gt;
    &lt;div class="card bg-dark text-white"&gt;
      &lt;img class="card-img" src="http://via.placeholder.com/300x340" alt="Card image"&gt;
      &lt;div class="card-img-overlay"&gt;
        &lt;h5 class="card-title"&gt;Title&lt;/h5&gt;
        &lt;h3 class="card-text font-weight-bold"&gt;&lt;span class="mr-auto"&gt;Some other title here&lt;/span&gt;&lt;/h3&gt;
        &lt;div class="align-self-end"&gt;Text I want at bottom&lt;/div&gt;
      &lt;/div&gt;
    &lt;/div&gt;
  &lt;/div&gt;</code></pre>
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  <p>I am unable to get the text in the last div by applying this class <code>align-self-end</code> to the bottom of the image. I understand that flex has been applied to the <code>.card-img-overlay</code> div with the direction of column then why am I unable to get the div to the bottom of the image? </p>