code: def resize(self, targ_sz, new_path='tmp', resume=True, fn=None):
          
          new_ds = []
          dls = [self.trn_dl,self.val_dl,self.fix_dl,self.aug_dl]
          if self.test_dl: dls += [self.test_dl, self.test_aug_dl]
          else: dls += [None,None]
          t = tqdm_notebook(dls)
          for dl in t: new_ds.append(self.resized(dl, targ_sz, new_path, resume, fn))
          t.close()
          return self.__class__(new_ds[0].path, new_ds, self.bs, self.num_workers, self.classes)
docs: Resizes all the images in the train, valid, test folders to a given size.
  
          Arguments:
          targ_sz (int): the target size
          new_path (str): the path to save the resized images (default tmp)
          resume (bool): if True, check for images in the DataSet that haven't been resized yet (useful if a previous resize
          operation was aborted)
          fn (function): optional custom resizing function