[python] add test Missing the important statement for Datetime in Python binding generation (#18175)

* [python] add test on datetime response import

* [python] update sample

* [python] update sample

samples/openapi3/client/petstore/python-pydantic-v1-aiohttp/docs/ImportTestDatetimeApi.md

@@ -0,0 +1,69 @@
+# petstore_api.ImportTestDatetimeApi
+
+All URIs are relative to *http://petstore.swagger.io:80/v2*
+
+Method | HTTP request | Description
+------------- | ------------- | -------------
+[**import_test_return_datetime**](ImportTestDatetimeApi.md#import_test_return_datetime) | **GET** /import_test/return_datetime | test date time
+
+
+# **import_test_return_datetime**
+> datetime import_test_return_datetime()
+
+test date time
+
+### Example
+
+```python
+import time
+import os
+import petstore_api
+from petstore_api.rest import ApiException
+from pprint import pprint
+
+# Defining the host is optional and defaults to http://petstore.swagger.io:80/v2
+# See configuration.py for a list of all supported configuration parameters.
+configuration = petstore_api.Configuration(
+    host = "http://petstore.swagger.io:80/v2"
+)
+
+
+# Enter a context with an instance of the API client
+async with petstore_api.ApiClient(configuration) as api_client:
+    # Create an instance of the API class
+    api_instance = petstore_api.ImportTestDatetimeApi(api_client)
+
+    try:
+        # test date time
+        api_response = await api_instance.import_test_return_datetime()
+        print("The response of ImportTestDatetimeApi->import_test_return_datetime:\n")
+        pprint(api_response)
+    except Exception as e:
+        print("Exception when calling ImportTestDatetimeApi->import_test_return_datetime: %s\n" % e)
+```
+
+
+
+### Parameters
+This endpoint does not need any parameter.
+
+### Return type
+
+**datetime**
+
+### Authorization
+
+No authorization required
+
+### HTTP request headers
+
+ - **Content-Type**: Not defined
+ - **Accept**: application/json
+
+### HTTP response details
+| Status code | Description | Response headers |
+|-------------|-------------|------------------|
+**200** | OK |  -  |
+
+[[Back to top]](#) [[Back to API list]](../README.md#documentation-for-api-endpoints) [[Back to Model list]](../README.md#documentation-for-models) [[Back to README]](../README.md)
+