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 __get_stop_condition(self):
        for covariance in self.__variances:
            if numpy.linalg.norm(covariance) == 0.0:
                return True