GitLab

Both conditional branches in `__init__` were executed, since `classes` for test
becomes a list and `if` was used instead of `elif`.

* Fix uninitialized instance variables

* Maintain consistency with other dataset classes

* Fix double assignment

* Fix initialization of self.classes

* add __repr__ for datasets

* fix lint

* Add documentation for transforms

* document and remove unused imports in mnist.py

* document lsun, mscoco datasets

* rest of the datasets documented

* Clean up the documentation in other functions

* Add links for datasets

* Add more documentation

* pep8 fix

    git ls-files | grep '\.py$' | xargs -n1 -P`nproc` autopep8 -i