Your link is dead… 404.
I am having the same problem as Vitaliy. In spite of many searches, I cannot find documentation for the change in how to import the FilesDataset class.
Works in older versions of fastai (apparently pre-1.0):
from fastai.conv_learner import *
from fastai.dataset import *
class MyClass(FilesDataset): …
But I can’t find the import for version 1.0.24. Please how does one import FilesDataset in the newest versions of fastai?