Changes in Text module of 1.0 library comparing to lesson 10

I am trying to follow changes in 1.0 text module comparing to what Jeremy presented in imdb.ipynb in lesson 10 of course 2 (2018).
And I do not succeed to trace some of the changes.
Did LanguageModelLoader() became LanguageModelPreLoader()?
But it does not responsible anymore for iterating over data set, right?
I also do not see anywhere in Fast 1.0 idea of randomly changing bptt size of batches that Jeremy demonstrated in the lecture. Do I miss something?