Hi, had the same issue.
After looking in to the predict functions/options it worked for me by manually generating a test dataset using the following specs:
# Let's assume our model receives input 0, and the target is 1
random_sample = (tensor([0]), tensor([1]))
# We need x number of samples (should be a multiple of the batch size you specified in the learner object, in the Notebook they suggest 64)
# Let us just replicate the random_sample tensor
test_data = [random_sample]*bs
# Use get_preds where dl points at a DataLoader object that we generate from our small test set
preds, targs = learn.get_preds(dl=DataLoader(dataset=test_data, bs=bs, shuffle=False, drop_last=False, num_workers=0))