title: Inserting column with insert method of pandas dataframe generating error
body: <p>I have below code</p>
  <p>I am trying to insert new columns as specific positions with <code>insert</code> method. Below is my code,</p>
  <pre><code>import pandas as pd
  
  (pd.DataFrame({'product name': ['laptop', 'printer', 'printer',], 'price': [1200, 150, 1200],  'price1': [1200, 150, 1200]})
      .insert(0, 'AAA', -1)
      .insert(1, 'BBB', -2)
  )
  </code></pre>
  <p>With this I am getting below error,</p>
  <pre><code>Traceback (most recent call last):
    File &quot;&lt;stdin&gt;&quot;, line 1, in &lt;module&gt;
  AttributeError: 'NoneType' object has no attribute 'insert'
  &gt;&gt;&gt;
  </code></pre>
  <p>Could you please help to resolve this error.</p>
  <p>Any pointer is highly appreciated.</p>