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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 check(cls):
 """ Verifies that all necessary values for the package to be used have been provided :raises: `elib_config._exc.IncompleteSetupError` """

        attribs = [
            'app_version',
            'app_name',
            'config_file_path',
            'config_sep_str',
        ]
        for attrib in attribs:
            if getattr(cls, attrib) == 'not_set':
                raise IncompleteSetupError(f'elib_config setup is incomplete; missing: {attrib}')