TypeError: The first input argument needs to be a sequence

when it is trying to train with the train_omniglot.py, i am hitting into this issue. can shed me some lights?

Traceback (most recent call last): File "train_omniglot.py", line 52, in for i, (images, labels) in train_generator: File "../utils/generators.py", line 44, in next return self.next() File "../utils/generators.py", line 53, in next for _img in zip(_images)] File "../utils/generators.py", line 53, in for _img in zip(_images)] TypeError: The first input argument needs to be a sequence