code: def _compute_delta_beta(self, df, events, start, stop, weights):
          
  
          score_residuals = self._compute_residuals(df, events, start, stop, weights) * weights[:, None]
  
          naive_var = inv(self._hessian_)
          delta_betas = -score_residuals.dot(naive_var) / self._norm_std.values
  
          return delta_betas
docs: approximate change in betas as a result of excluding ith row