Format stats before printing.

def format_stats(self, stats:TensorOrNumList)->None:
        "Format stats before printing."
        str_stats = []
        for name,stat in zip(self.names,stats):
            str_stats.append('#na#' if stat is None else str(stat) if isinstance(stat, int) else f'{stat:.6f}')
        if self.add_time: str_stats.append(format_time(time() - self.start_epoch))
        if not self.silent: self.pbar.write(str_stats, table=True)