hello community 
need help, I'm working with the version of OpenERP and I 8rc1 encuantro with changes in coding of susu modules in which I'm working is to account /account.invoice.py where I have seen that has the following @api. v7-@api.v8 as use and a different way of creating the fields, 
indicating I could help with the classes @api understand is that they are updating old code version of OpenERP to create new features in the new version of OpenERP. 
which is the functionality that performs the function 
@api