def __init__(self, groups=None):
        super(GroupedRequirements, self).__init__(NamedRequirements)
        self.groups = groups or self.default_groups
        self.filename = None
        self.create_default_groups()
def __extract_clusters(self):
        self.__clusters = [[] for _ in range(self.__amount_clusters)]
        for index_point in range(len(self.__data)):
            candidates = []
            for index_cluster in range(self.__amount_clusters):
                candidates.append((index_cluster, self.__rc[index_cluster][index_point]))