title: Remove duplicate rows from a pandas dataframe: Case Insenstive comparison
body: <p>I want to remove duplicate rows from the dataframe based on values in two columns: <code>Column1</code> and <code>Column2</code></p>
  
  <p>If <code>dataframe</code> is:</p>
  
  <pre><code>df = pd.DataFrame({'Column1': ["'cat'", "'toy'", "'cat'"],
                     'Column2': ["'bat'", "'flower'", "'bat'"],
                     'Column3': ["'xyz'", "'abc'", "'lmn'"]})
  </code></pre>
  
  <p>On using:</p>
  
  <pre><code>result_df = df.drop_duplicates(subset=['Column1', 'Column2'], keep='first')
  print(result_df)
  </code></pre>
  
  <p>I get:</p>
  
  <pre><code>  Column1   Column2 Column3
  0   'cat'     'bat'   'xyz'
  1   'toy'  'flower'   'abc'
  </code></pre>
  
  <p>But using same code for <code>dataframe</code> (Cat and Bat cases changed)</p>
  
  <pre><code>df = pd.DataFrame({'Column1': ["'Cat'", "'toy'", "'cat'"],
                     'Column2': ["'Bat'", "'flower'", "'bat'"],
                     'Column3': ["'xyz'", "'abc'", "'lmn'"]})
  </code></pre>
  
  <p>I get:</p>
  
  <pre><code>  Column1   Column2 Column3
  0   'Cat'     'Bat'   'xyz'
  1   'toy'  'flower'   'abc'
  2   'cat'     'bat'   'lmn'
  </code></pre>
  
  <p>Expected Output:</p>
  
  <pre><code>  Column1   Column2 Column3
  0   'cat'     'bat'   'xyz'
  1   'toy'  'flower'   'abc'
  </code></pre>
  
  <p>How can this comparison be done case insensitively?</p>