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 __normalize_probabilities(self):
        for index_point in range(len(self.__data)):
            probability = 0.0
            for index_cluster in range(len(self.__clusters)):
                probability += self.__rc[index_cluster][index_point]