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 initialize(self, init_type = ema_init_type.KMEANS_INITIALIZATION):
        """!
        @brief Calculates initial parameters for EM algorithm: means and covariances using
                specified strategy.