title: df.to_dict make duplicated index (pandas) as primary key in a nested dict
body: <p>I have this data frame which I'd like to convert to a dict in python, I have many other categories, but showed just two for simplicity</p>
  <pre><code>Category   Name                     Description             Price       
  Diesel     Land Rover               No Description found    £ x
  Electric   Tesla Model X            No Description found    £ x
  </code></pre>
  <p>I want the output to be like this</p>
  <pre><code>dict = {&quot;Category&quot;: {&quot;Diesel&quot; : {
                                  &quot;Name&quot;: &quot;Land Rover&quot;, 
                                  &quot;Description&quot;:&quot;No Description Found&quot;, 
                                  &quot;Price&quot;: &quot;£ x&quot; },
                                             
                      &quot;Electric&quot; : {&quot;Name&quot;: &quot;Tesla Model X&quot;, 
                                    &quot;Description&quot;:&quot;No Description Found&quot;, 
                                    &quot;Price&quot;: &quot;£ x&quot; }
                      }               
          }
  </code></pre>