GitLab

* Fixing mypy errors.

* Fixing typing issue.

* remove sys.version_info == 2

* remove sys.version_info < 3

* remove from __future__ imports

* fixed call to the VisionDataset constructor

* change call from keyword arguments to positional

* changed order of arguments

* removed transforms argument once again

* Fixed call to constructor of parent class

* fixed LSUN

* fixed Caltech256

The backslash should be escaped. Currently, [it](https://pytorch.org/docs/master/torchvision/datasets.html#usps) looks bad:

* add USPS dataset

* minor fixes

* Improvements to the USPS dataset

Add it to the documentation, expose it to torchvision.datasets
and inherit from VisionDataset