neg methods and bugfix#253

Merged

Dr-Irv merged 3 commits intopandas-dev:mainfrom

amotzop:neg_methods

Sep 2, 2022

Commits on Sep 2, 2022

Added __neg__ to Series, DataFrame and Index. Fixed bug in Index.difference
Amotz
committed
Moved to NDFrameT and IndexT
Amotz
committed
sorted imports
Amotz
committed