title: Convert boolean to string in DataFrame
body: <p>Stems from <a href="https://stackoverflow.com/questions/42788713/pandas-mapping-to-true-false-as-string-not-boolean">this</a> post, but I have found a little issue with the solution.</p>
  
  <p>Using <code>df = df.replace({True: 'TRUE', False: 'FALSE'})</code>, if a value is <code>1</code> or <code>0</code> it will be replaced. I only want to replace values that are actually <code>True</code> or <code>False</code> of <code>&lt;class 'bool'&gt;</code>.</p>
  
  <p>How can I do this?</p>