Hello Fazal Haleem

As we know product_template have no relation with purchase_order_line directly you could below code and it will show you related purchase order line in product_template view.

class purchase_order_line(models.Model):
    _inherit = "purchase.order.line"
    product_template_id=fields.Many2one("product.template",related="product_id.product_tmpl_id")

class product_template(models.Model):
    _inherit = "product.template"
    purchase_line_ids = fields.One2many("purchase.order.line","product_template_id")

Now you can put purchase_line_ids fields in product template view.

Hope this will Help you.

Thanks,

Husain