human
Solve the following python programming problem given the following code:
@ pytest.fixture 
def mock_folder() : 
    folder = { 
        'display_name' : 'My Folder', 
        'id' : 'anuep8pe5ug3xrupchwzba2o8', 
        'name' : None, 
        'account_id' : MOCK_ACCOUNT_ID, 
        'object' : 'folder', 
} 
    response_body = json.dumps (folder) 
    endpoint = re.compile ((API_URL + '/folders/anuep8pe5ug3xrupchwzba2o8')) 
    responses.add (responses.GET, endpoint, content_type = 'application/json', status = 200, body = response_body) 
    def request_callback(request) : 
        payload = json.loads (request.body) 
        if ('display_name' in payload) : 
            folder.update (payload) 
return (200, { 
            
}, json.dumps (folder)) 
responses.add_callback (responses.PUT, endpoint, content_type = 'application/json', callback = folder) 

    
    

    Fix the buggy line: responses.add_callback (responses.PUT, endpoint, content_type = 'application/json', callback = folder)
assistant
#Here is Python code to fix the buggy line: responses.

responses.add_callback (responses.PUT, endpoint, content_type = 'application/json', callback = def request_callback()