ARGOMENTO: Field one2many obbligatorio (required)

class product_template(osv.osv):
	_inherit = 'product.template'
	_name = 'product.template'
	
	_columns = {
            'seller_ids': fields.one2many('product.supplierinfo', 'product_tmpl_id', 'Supplier', required=True),
            }
product_template()

def create(self, cr, uid, vals, context=None):
        ''' Store the initial standard price in order to be able to retrieve the cost of a product template for a given date'''
        product_template_id = super(product_template, self).create(cr, uid, vals, context=context)
        if not context or "create_product_product" not in context:
            self.create_variant_ids(cr, uid, [product_template_id], context=context)
        self._set_standard_price(cr, uid, product_template_id, vals.get('standard_price', 0.0), context=context)

        # TODO: this is needed to set given values to first variant after creation
        # these fields should be moved to product as lead to confusion
        related_vals = {}
        if vals.get('ean13'):
            related_vals['ean13'] = vals['ean13']
        if vals.get('default_code'):
            related_vals['default_code'] = vals['default_code']
        if related_vals:
            self.write(cr, uid, product_template_id, related_vals, context=context)

        return product_template_id

if not vals.get('seller_ids')