How can I migrate this code to the versión 8?? How can I get the "ids" variable?   

def _get_image(self, cr, uid, ids, context=None):
        result = dict.fromkeys(ids, False)
        for obj in self.browse(cr, uid, ids, context=context):
            result[obj.id] = tools.image_get_resized_images(obj.image, avoid_resize_medium=True)
        return result
  
    def _set_image(self, cr, uid, id, name, value, context=None):
        return self.write(cr, uid, [id], {'image': tools.image_resize_image_big(value)}, context=context)    
 
    _columns = {
        'image': fields.binary("Image", help="This field holds the image used as image for the category, limited to 1024x1024px."),
        'image_medium': fields.function(_get_image, fnct_inv=_set_image,
            string="Medium-sized image", type="binary", multi="_get_image",
            store={
                'product.template': (lambda self, cr, uid, ids, c={}: ids, ['image'], 10),
            },
            help="Medium-sized image of the category. It is automatically "\
                 "resized as a 128x128px image, with aspect ratio preserved. "\
                 "Use this field in form views or some kanban views."),

    }

thanks