Possible documentation problem in GroupBy section
Hi.  I'm not understanding the following section in the pandas doc regarding "Flexible apply" on the following page:  http://pandas.pydata.org/pandas-docs/stable/groupby.html:  Is the python error about missing parentheses (I suppose a v2 to v3 issue with print) intended to be the explanatory result?  If so, it seems confusing in this context.  Is this a bug in the code that is generating the example for the doc.  Thanks. 

<img width="735" alt="screen shot 2017-08-27 at 8 36 03 am" src="https://user-images.githubusercontent.com/3465912/29751641-f4a0ea2a-8b04-11e7-8fda-b1aa96d1935e.png">



