def package_listing(c):
    """
    Return a nicely parsed package-group listing 
    """
    result = {}
    for group, object in c._groups.iteritems():
        mandatory = object.mandatory_packages.keys()
        default = object.default_packages.keys()
        optional = object.optional_packages.keys()
        result[group] = [mandatory, default, optional]
    return result
