add relation model

my_library/models/relation.py

@@ -0,0 +1,25 @@
+from odoo import models, fields
+
+
+class ChildModel1(models.Model):
+    _name = 'child1.model'
+
+    parent_id = fields.Many2one(comodel_name='parent1.model', string='Parent')
+
+
+class ParentModel1(models.Model):
+    _name = 'parent1.model'
+
+    child_ids = fields.One2many(comodel_name='child1.model', inverse_name='parent_id', string='Children')
+
+
+class ChildModel2(models.Model):
+    _name = 'child2.model'
+
+    parent_id = fields.Many2many(comodel_name='parent2.model', string='Parent')
+
+
+class ParentModel2(models.Model):
+    _name = 'parent2.model'
+
+    child_ids = fields.Many2many(comodel_name='child2.model', string='Children')