- use this method in BPMInvoiceTransactionRule to avoid code repetition
 - set property_sheets explicitly on each class (inheritance for property_sheet property is not working?)


git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@28249 20353a03-c40f-0410-a6d1-a30d3c3de9de