Exception: Call project.prepare() first: in lesson3-rsna-pneumonia-detection-mdai-client-lib

[tobimichigan]

Hi there,
I was testing lesson3-rsna-pneumonia-detection-mdai-client-lib, and encountered an issue on this sectionof the code:

train_dataset, valid_dataset = mdai.common_utils.train_test_split(dataset)

error encountered is as follows:

`Exception Traceback (most recent call last)
in ()
----> 1 train_dataset, valid_dataset = mdai.common_utils.train_test_split(dataset)

1 frames
/usr/local/lib/python3.6/dist-packages/mdai/preprocess.py in get_image_ids(self, verbose)
296 """
297 if not self.image_ids:
--> 298 raise Exception("Call project.prepare() first.")
299
300 if verbose:

Exception: Call project.prepare() first.`

Meanwhile:
dataset = p.get_dataset_by_id('D_VolK4E') dataset.prepare()

had already been executed.

Any clues?