code: def cumulative_distribution(self, X, U=0):
          
          self.check_fit()
  
          low_bounds = self.model.dataset.mean() - (5 * self.model.dataset.std())
          return self.model.integrate_box_1d(low_bounds, X) - U
docs: Computes the integral of a 1-D pdf between two bounds
  
          Args:
              X(float): a datapoint.
              U(float): cdf value in [0,1], only used in get_ppf
  
          Returns:
              float: estimated cumulative distribution.