[PYTHON] Setting default value for Required variables (#10809)

* [req_vars_changes]

* Added new schema to generate samples to test the issue mentioned in the PR.

* Changed the variable name from setRequiredVars to initRequiredVars

* Added initRequiredVars as a generator additional property

* Regenerating the samples after rebasing the code with master branch

* Changed the description of additional property

samples/client/petstore/python/test/test_triangle.py

@@ -0,0 +1,39 @@
+"""
+    OpenAPI Petstore
+
+    This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\  # noqa: E501
+
+    The version of the OpenAPI document: 1.0.0
+    Generated by: https://openapi-generator.tech
+"""
+
+
+import sys
+import unittest
+
+import petstore_api
+from petstore_api.model.polygon import Polygon
+from petstore_api.model.triangle_all_of import TriangleAllOf
+globals()['Polygon'] = Polygon
+globals()['TriangleAllOf'] = TriangleAllOf
+from petstore_api.model.triangle import Triangle
+
+
+class TestTriangle(unittest.TestCase):
+    """Triangle unit test stubs"""
+
+    def setUp(self):
+        pass
+
+    def tearDown(self):
+        pass
+
+    def testTriangle(self):
+        """Test Triangle"""
+        # FIXME: construct object with mandatory attributes with example values
+        # model = Triangle()  # noqa: E501
+        pass
+
+
+if __name__ == '__main__':
+    unittest.main()