docs: def _get_bin_width(stdev, count):
      """Return the histogram's optimal bin width based on Sturges
  
      http://www.jstor.org/pss/2965501
      """
  
      w = int(round((3.5 * stdev) / (count ** (1.0 / 3))))
      if w:
          return w
      else:
          return 1