totic variance of point estimates of the survival function have been proposed in the literature. Where available, those can be calculated and added to the output object using <code>conf_int=TRUE</code>. It is however recommended to use bootstrapping to estimate the variance instead, which can be done by setting <code>bootstrap=TRUE</code>. The <code>n_boot</code> argument is set to 500 by default. This number was chosen because it worked well in simulations but it does not guarantee convergence in practice.