A possible bug in style style sheets reference
I found a possible bug in the code in this page. I copied and pasted the code into my Notebook, it returns an error: TypeError: set_ticks() got an unexpected keyword argument ‘labels’. The error noted is in line 42. It was ax.set_xticks(x + width, labels=['a', 'b', 'c', 'd', 'e']), I changed it to ax.set_xticks(x + width, ) \ ax.set_xticklabels(['a', 'b', 'c', 'd', 'e']), then it works.
The labels keyword is new. You are likely using an older version of Matplotlib.