[python-nextgen] Fix binary response (#15076)

* fix binary response in python nextgen client

* update samples

samples/client/echo_api/python-nextgen/docs/BodyApi.md

@@ -4,10 +4,71 @@ All URIs are relative to *http://localhost:3000*
 
 Method | HTTP request | Description
 ------------- | ------------- | -------------
+[**test_binary_gif**](BodyApi.md#test_binary_gif) | **POST** /binary/gif | Test binary (gif) response body
 [**test_echo_body_pet**](BodyApi.md#test_echo_body_pet) | **POST** /echo/body/Pet | Test body parameter(s)
 [**test_echo_body_pet_response_string**](BodyApi.md#test_echo_body_pet_response_string) | **POST** /echo/body/Pet/response_string | Test empty response body
 
 
+# **test_binary_gif**
+> bytearray test_binary_gif()
+
+Test binary (gif) response body
+
+Test binary (gif) response body
+
+### Example
+
+```python
+from __future__ import print_function
+import time
+import os
+import openapi_client
+from openapi_client.rest import ApiException
+from pprint import pprint
+# Defining the host is optional and defaults to http://localhost:3000
+# See configuration.py for a list of all supported configuration parameters.
+configuration = openapi_client.Configuration(
+    host = "http://localhost:3000"
+)
+
+
+# Enter a context with an instance of the API client
+with openapi_client.ApiClient(configuration) as api_client:
+    # Create an instance of the API class
+    api_instance = openapi_client.BodyApi(api_client)
+
+    try:
+        # Test binary (gif) response body
+        api_response = api_instance.test_binary_gif()
+        print("The response of BodyApi->test_binary_gif:\n")
+        pprint(api_response)
+    except Exception as e:
+        print("Exception when calling BodyApi->test_binary_gif: %s\n" % e)
+```
+
+### Parameters
+This endpoint does not need any parameter.
+
+### Return type
+
+[**bytearray**](bytearray.md)
+
+### Authorization
+
+No authorization required
+
+### HTTP request headers
+
+ - **Content-Type**: Not defined
+ - **Accept**: image/gif
+
+### HTTP response details
+| Status code | Description | Response headers |
+|-------------|-------------|------------------|
+**200** | Successful operation |  -  |
+
+[[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)
+
 # **test_echo_body_pet**
 > Pet test_echo_body_pet(pet=pet)