title: pandas dataframe index: to_list() vs tolist()
body: <p>I recently wrote a python script for someone, where I converted a pandas dataframe's index into a list using <code>to_list()</code>. However, this does not work for them, as they get: <code>AttributeError: 'Index' object has no attribute 'to_list'</code> with their python interpretter.</p>
  
  <p>I did some searching and found that there is also <code>tolist()</code> that seems to do the same as <code>to_list()</code>: searching on <a href="https://pandas.pydata.org/pandas-docs/stable/" rel="noreferrer">Pandas documentation</a> finds both, with word-for-word identical description.
  On the other hand, the <a href="https://pandas.pydata.org/pandas-docs/stable/reference/indexing.html" rel="noreferrer">documentation of Index</a> mentions only <code>to_list()</code>.</p>
  
  <p>So I wonder whether there is a difference between the two</p>
  
  <ul>
  <li>in functionality</li>
  <li>in popularity and/or "officiality"/endorsement</li>
  <li>in support in different version of pandas</li>
  </ul>