I want to override the picking_type_id value in purchase.order to be not required & not default value ,i tried doing this but it's not working :

_columns = {
'picking_type_id': fields.many2one(
'stock.picking.type',
'Deliver To',
help="This will determine picking type of incoming shipment",
required=False,
states={'confirmed': [('readonly', False)], 'approved': [('readonly', False)], 'done': [('readonly', True)]}),
} 

then i tried to  add      {'required': '0'}    to xml vue but i got a js bug 

Edit : 

I did the non required part ,it was simple  just adding required = "0" 

Now i'm stuck with the default part