code: def plot(self, normed=False, scale_errors_by=1.0, scale_histogram_by=1.0, plt=plt, errors=False, **kwargs):
          
          if not CAN_PLOT:
              raise ValueError("matplotlib did not import, so can't plot your histogram...")
          if errors:
              kwargs.setdefault('linestyle', 'none')
              yerr = np.sqrt(self.histogram)
              if normed:
                  y = self.normalized_histogram
                  yerr /= self.n
              else:
                  y = self.histogram.astype(np.float)
              yerr *= scale_errors_by * scale_histogram_by
              y *= scale_histogram_by
              plt.errorbar(self.bin_centers, y, yerr,
                           marker='.', **kwargs)
          else:
              kwargs.setdefault('linestyle', 'steps-mid')
              plt.plot(self.bin_centers, self.histogram, **kwargs)
docs: Plots the histogram with Poisson (sqrt(n)) error bars
            - scale_errors_by multiplies the error bars by its argument
            - scale_histogram_by multiplies the histogram AND the error bars by its argument
            - plt thing to call .errorbar on (pylab, figure, axes, whatever the matplotlib guys come up with next)