Except, you can’t do anything with this databunch object. 'TensorDataset' object has no attribute 'c'
And your code is missing:
from sklearn.model_selection import train_test_split
as @sgugger said, you have to implement your own Dataset class. It appears from this thread that a new method from_array() would be a useful addition to the fastai library.
data = (ItemList.from_array(train_ds = train_array, valid_ds=valid_array, test_ds=test_array), ...)