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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 __load_paths(self, base_path=None):
 """ Set the paths of the different folders """

        if base_path is None:
            base_path = dirname(dirname(dirname(__file__)))
        if not base_path.endswith(sep):
            base_path += sep
        self.__paths = {
            'base': base_path,
            'cert': base_path + 'certs' + sep,
            'lib': base_path + 'lib' + sep,
            'extlib': base_path + 'extlib' + sep,
        }