The purpose of the implementation is to create a module that contains a model (purchase.order.line) with a custom field (x_quotation_number):

Module structure:

__manifest__.py 

__init__.py

models 

     __init__.py

    purchase_order_line_inherit.py

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Content of each file:

__manifest__.py:
# -*- coding: utf-8 -*-

{ 
‘name’: ‘Quotation Number Implementation’,

 ‘version’: ‘1.0’,

 ‘category’: ‘Sales/Purchases’, 

‘summary’: “Implementation of ‘Quotation Number’ field.”,

 ‘description’: “”" Implementation of ‘Quotation Number’ field in module ‘purchase.order.line’; “”", ‘depends’: [‘base’, ‘purchase’], 

‘installable’: True

}

__init__.py:
# -*- coding: utf-8 -*-

from . import models

models/init.py:
from . import purchase_order_line_inherit

models/purchase_order_line_inherit.py: 
from odoo import fields, models

class PurchaseOrderLineInherit(models.Model):
    _inherit = ‘purchase.order.line’ 
    quotation_number = fields.Char(string=“Quotation Number”)


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Upon importing, it is verified in the fields of the ‘purchase.order.line’ model that the custom field was not added.