def save_checkpoint(self,
                        out_dir,
                        filename_tmpl='iter_{}.pth',
                        meta=None,
                        save_optimizer=True,
                        create_symlink=False):
        """Save checkpoint to file.

        Args:
            out_dir (str): Directory to save checkpoint files.
            filename_tmpl (str, optional): Checkpoint file template.
                Defaults to 'iter_{}.pth'.
            meta (dict, optional): Metadata to be saved in checkpoint.
                Defaults to None.
            save_optimizer (bool, optional): Whether save optimizer.
                Defaults to True.
            create_symlink (bool, optional): Whether create symlink to the
                latest checkpoint file. Defaults to True.
        """
        if meta is None:
            meta = dict(iter=self.iter + 1, epoch=self.epoch + 1)
        elif isinstance(meta, dict):
            meta.update(iter=self.iter + 1, epoch=self.epoch + 1)
        else:
            raise TypeError(
                f'meta should be a dict or None, but got {type(meta)}')
        if self.meta is not None:
            meta.update(self.meta)

        filename = filename_tmpl.format(self.iter + 1)
        filepath = osp.join(out_dir, filename)
        optimizer = self.optimizer if save_optimizer else None
        save_checkpoint(self.model, filepath, optimizer=optimizer, meta=meta)
        # in some environments, `os.symlink` is not supported, you may need to
        # set `create_symlink` to False
        # if create_symlink:
        #     dst_file = osp.join(out_dir, 'latest.pth')
        #     if platform.system() != 'Windows':
        #         mmcv.symlink(filename, dst_file)
        #     else:
        #         shutil.copy(filepath, dst_file)
Save checkpoint to file.

        Args:
            out_dir (str): Directory to save checkpoint files.
            filename_tmpl (str, optional): Checkpoint file template.
                Defaults to 'iter_{}.pth'.
            meta (dict, optional): Metadata to be saved in checkpoint.
                Defaults to None.
            save_optimizer (bool, optional): Whether save optimizer.
                Defaults to True.
            create_symlink (bool, optional): Whether create symlink to the
                latest checkpoint file. Defaults to True.
        
EVA-02/seg/mmcv_custom/apex_runner/apex_iter_based_runner.py