title: Pandas return column data as list without duplicates
body: <p>This is just an oversimplification but I have this large categorical data.</p>
  <pre><code>Name   Age Gender 
  John    12 Male 
  Ana     24 Female
  Dave    16 Female
  Cynthia 17 Non-Binary
  Wayne   26 Male
  Hebrew  29 Non-Binary
  </code></pre>
  <p>Suppose that it is assigned as <code>df</code> and I want it to return as a list with non-duplicate values:</p>
  <pre><code>'Male','Female','Non-Binary'
  </code></pre>
  <p>I tried it with this code, but this returns the gender with duplicates</p>
  <pre><code>list(df['Gender'])
  </code></pre>
  <p>How can I code it in pandas so that it can return values <strong>without duplicates</strong>?</p>