title: How to get Case Insensitive Python SET
body: <p>I have a list of strings:</p>
  
  <pre><code>In [53]: l = ['#Trending', '#Trending', '#TrendinG', '#Yax', '#YAX', '#Yax']
  
  In [54]: set(l)
  Out[54]: {'#TrendinG', '#Trending', '#YAX', '#Yax'}
  </code></pre>
  
  <p>I want to have a <em>case-insensitive</em> <code>set</code> of this list.</p>
  
  <p><strong>Expected Result:</strong></p>
  
  <pre><code>Out[55]: {'#Trending', '#Yax'}
  </code></pre>
  
  <p>How can I achieve this?</p>