i have model purchase.request the user enter product line in line_ids one2many field for  this model the user can create purchase order with products inserted in the line_ids in purchase.request model, the user can delete one line from order_lines in purchase,order.

how can i check if the line_ids from purchase.request model is existing in order_line in purchase.order model,

i have 3 model:

purchase.request.line linked with purchase.request using request_id.

and purchase.order linked with purchase.request using request_ids many2many field.

i try this code:

for rec in self:
    purchase_orders = self.env['purchase.order'].search([('request_ids', 'in', rec.id)])
    for order_line in purchase_orders.order_line:
        for line in rec.line_ids:
            if line.product_id in order_line:
                rec.line_ids.purchase_state = 'rfq'

but i get below error:

TypeError: Mixing apples and oranges: product.product(1549,) in purchase.order.line(1570,)

Thanks .....