code: def crb(self, params=None, *args, **kwargs):
          
          fish = self.fisherinformation(params=params, *args, **kwargs)
          return np.sqrt(np.diag(np.linalg.inv(fish))) * self.sigma
docs: Calculate the diagonal elements of the minimum covariance of the model
          with respect to parameters params. ``*args`` and ``**kwargs`` go to
          ``fisherinformation``.