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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 _get_users_of_group(config, group):
 """ Utility to query fas for users of a group. """

    if not group:
        return set()
    fas = fmn.rules.utils.get_fas(config)
    return fmn.rules.utils.get_user_of_group(config, fas, group)