code: def std(self, bessel_correction=True):
          
          if bessel_correction:
              n = self.n
              bc = n / (n - 1)
          else:
              bc = 1
          return np.sqrt(np.average((self.bin_centers - self.mean) ** 2, weights=self.histogram)) * bc
docs: Estimates std of underlying data, assuming each datapoint was exactly in the center of its bin.