product.py

from openerp.osv.orm import Model
from openerp.osv import fields
from openerp.osv.osv import except_osv
from openerp.tools.translate import _


class product_category(Model):
    _inherit = "product.category"
    _columns = {
        'attribute_group_ids': fields.many2many('attribute.group', 'categ_attr_grp_rel', 'categ_id', 'grp_id', 'Attribute Groups'),
        }


class product_product(Model):
    _inherit = "product.product"

    def _attr_grp_ids(self, cr, uid, ids, field_names, arg=None, context=None):
        res = {}
        for product in self.browse(cr, uid, ids, context=context):
            grp_ids = [grp.id for grp in product.categ_id.attribute_group_ids]
            for categ in product.categ_ids:
                grp_ids += [grp.id for grp in categ.attribute_group_ids]
            res[product.id] = list(set(grp_ids))
        return res