I have two model, purchase.pi and purchase.order

I have order lines in purchase.pi

Now, I'm trying to get the order lines from purchase.pi and populate the order lines of purchase.order model, based on the selection of order_id. The order_id can be one or more, and order lines will be added one after another.

But, the problem is after selecting the second order_id I get its own order lines and the previously selected order line again.
Below is my code:

	​	​
class PurhcasePi(models.Model):
	​_name="purchase.order.pi.copy"
	​_inherit= ['purchase.order','mail.thread', 'mail.activity.mixin']
	​_description="Purchase order copy"

	​order_line= fields.One2many('purchase.order.pi.line.copy', 'order_id', string='Order Lines', states={'cancel': [('readonly', True)], 'done': [('readonly', True)]}, copy=True)
	​lc_id= fields.Many2one('purchase.order', string='LC')

	​def_create_lc_lines_context(self, lc_id):
		​​lines= []
	​	​for line in self.order_line:
	​		​​if line.product_qty >0:
	​	​		​​lines.append(
	​	​	​		​​(0, 0, {
	​	​	​			​​​'product_id': line.product_id.id,
	​	​	​	​	​	​'name': line.name,
	​	​	​	​	​	​'product_uom':line.product_uom,
	​	​	​	​	​	​'price_unit':line.price_unit,
	​	​	​	​	​	​'price_subtotal':line.price_subtotal,
	​	​	​	​	​	​'product_qty': line.product_qty,
	​                    		​​}
	​                	​))
	​	​	​else:
	​	​	​	​continue
	​	​return lines



class lc(models.Model):
	​_inherit='purchase.order'
	​
	​pi_ids= fields.One2many('purchase.order.pi.copy','lc_id', string='Proforma Invoices')

	​
	​@api.onchange('pi_ids')
	​def _onchange_pi_ids(self):
	​	​if self.pi_ids:
	​	​	​order_line=self.pi_ids._create_lc_lines_context(self.pi_ids.order_line)
	​	​	​self.order_line=order_line



The marked order lines are repeated from PI00006.