I'm trying to look for qty_available of a product into a specified partner location, I have three Many2one fields to res.partner,

    printer_book_block = fields.Many2one('res.partner', string="Printer Book Block")
    printer_binding = fields.Many2one('res.partner', string="Printer Binding")
    printer_edging = fields.Many2one('res.partner', string="Printer Edging")

So, on the lines of this model I should look for those quantities, depending on which res.partner Many2one has been selected:

    order_lines = fields.One2many('bsi.print.order.lines', 'print_order', string="Order lines")

    @api.multi
    @api.constrains('order_lines', 'order_lines.isbn')
    def check_quantity(self):
        location = self.printer_book_block.property_stock_supplier.id
        for rec in self:
            if rec.order_lines:
                for line in rec.order_lines:
                    if line.qty > line.isbn.qty_available in location:
                        rec.write({'state': 'awaitingraw'})
                    else:
                        rec.write({'state': 'work_in_progress',},)

This method should look for qty_available on printer_book_block.property_stock_supplier, but it seems like it doesn't really look for that particular location.

The field property_stock_supplier is a field which is part of res.partner model, and it specifies the location for every partner as supplier on the system.

Also, how can I specify if one res.partner has been selected to look specifically for it?

Any ideas?

PS = isbn is a Many2one to product.product