StopIteration

hello
when i train i have below error?
call reset()
/usr/local/lib/python3.5/dist-packages/mxnet/module/base_module.py:505: UserWarning: Optimizer created manually outside Module but rescale_grad is not normalized to 1.0/batch_size/num_workers (1.0 vs. 0.0078125). Is this intended?
optimizer_params=optimizer_params)
Traceback (most recent call last):
File "train.py", line 379, in
main()
File "train.py", line 376, in main
train_net(args)
File "train.py", line 371, in train_net
epoch_end_callback = epoch_cb )
File "/usr/local/lib/python3.5/dist-packages/mxnet/module/base_module.py", line 523, in fit
next_data_batch = next(data_iter)
File "/usr/local/lib/python3.5/dist-packages/mxnet/io/io.py", line 228, in __next__
return self.next()
File "/usr/local/lib/python3.5/dist-packages/mxnet/io/io.py", line 474, in next
raise StopIteration
StopIteration