title: Pandas' sort_values function not working as intended?
body: <p>I have this dataframe that consists of 6 columns, and I'm trying to sort on the "Sample Type" column.
  My dataframe looks like this:</p>
  
  <pre><code>df = pd.DataFrame({'Sample ID': [1,2,3], 'Sample Type':[Metastatis, Metastasis, Primary],
  })
  </code></pre>
  
  <p>I've used the sort_values() function as follows:</p>
  
  <pre><code>df.sort_values(by = ['Sample Type'])
  </code></pre>
  
  <p>What I expect to see is the dataframe becomes sorted on the Sample Type column, returning the dataframe sorted in alphabetical order.
  However, what gets returned is that dataframe with alternating Sample Types, which clearly indicates that the sorting that I'm expecting hasn't occurred.</p>
  
  <p>Am I using the function incorrectly? Please point out any errors that I'm overlooking. Thank you</p>