remove private functions whose responsibilities have been subsumed by datapipes. TODO: migrate WMT14 to remove remaining private dataset utils. (#1564)
remove private functions whose responsibilities have been subsumed by datapipes. TODO: migrate WMT14 to remove remaining private dataset utils. (#1564)

* remove private functions whose responsibilities have been subsumed by datapipes.

* remove unused imports.
pytorch/text,pytorch/text,pytorch/text,pytorch/text