When I start the train_rcnn.py, I get the following error, can you tell me what the reason is：

File "train_rcnn.py", line 275, in
lr_scheduler_each_iter = (cfg.TRAIN.OPTIMIZER == 'adam_onecycle')
File "D:\Anaconda3\EPNet\tools..\tools\train_utils\train_utils.py", line 197, in train
loss, tb_dict, disp_dict = self._train_it(batch)
File "D:\Anaconda3\EPNet\tools..\tools\train_utils\train_utils.py", line 130, in _train_it
loss, tb_dict, disp_dict = self.model_fn(self.model, batch)
File "D:\Anaconda3\EPNet\tools..\lib\net\train_functions.py", line 37, in model_fn
img = torch.from_numpy(data['img']).cuda(non_blocking = True).float().permute((0, 3, 1, 2))
KeyError: 'img'