Create tree view to show all component but bom_id colum empty no show data

class StockMoveLine(models.Model):   

 _inherit = "stock.move.line"

    prod_bill= fields.Many2one("mrp.bom", related='product_id.bom_id', string="Bill Of Material")
    to_con = fields.Float(related='move_id.product_uom_qty', store=True)    

actual = fields.Float(related='move_id.quantity_done', store=True, string='actual')
    diffrent = fields.Integer(string='diffrent', compute='_compute_due_dif', store=True)

    @api.depends('to_con', 'actual')
    def _compute_due_dif(self):
        for record in self:
            if record.to_con:
                dif = record.to_con - record.actual
                record.diffrent = dif