code: def probability_in(self, a, b):
          
          if self.mean is None:
              return
          p1 = normdist(x=a, mu=self.mean, sigma=self.standard_deviation)
          p2 = normdist(x=b, mu=self.mean, sigma=self.standard_deviation)
          return abs(p1 - p2)
docs: Returns the probability of a random variable falling between the given
          values.