docs: def rmse(params1, params2):
      r"""Compute the root-mean-squared error between two models.
  
      Parameters
      ----------
      params1 : array_like
          Parameters of the first model.
      params2 : array_like
          Parameters of the second model.
  
      Returns
      -------
      error : float
          Root-mean-squared error.
      """
      assert len(params1) == len(params2)
      params1 = np.asarray(params1) - np.mean(params1)
      params2 = np.asarray(params2) - np.mean(params2)
      sqrt_n = math.sqrt(len(params1))
      return np.linalg.norm(params1 - params2, ord=2) / sqrt_n