def __str__(self):
        return "".join([self.package, self.version or ""])
def __update_covariance(self, means, rc, mc):
        covariance = 0.0
        for index_point in range(len(self.__data)):
            deviation = numpy.array([self.__data[index_point] - means])
            covariance += rc[index_point] * deviation.T.dot(deviation)