stock: inventory uses self in classmethods

http://hg.tryton.org/trytond/trytond/modules/stock/file/1e780a9b1aed/inventory.py#l128

added easy + 1 deleted label

The attached review fixes it

assigned to @pokoli

added type::feature + 1 deleted label and removed 1 deleted label

New changeset dfe734ea3eb5 by Sergi Almacellas Abellana in branch 'default':
Use cls in classmethods
http://hg.tryton.org/modules/stock/rev/dfe734ea3eb5

added 1 deleted label and removed 1 deleted label

closed