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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def create_disposable_app(clientInfo, config={}):
 """ Use an existing disposable app if data exists or create a new one and persist the data. """

    file = _get_disposable_app_filename(clientInfo)
    existing = _get_existing_disposable_app(file, clientInfo, config)
    if existing:
        if _check_app_is_valid(existing):
            return existing
        else:
            print("Existing client has expired, must recreate.")
        
    return _create_new_disposable_app(file, clientInfo, config)