def __missing__(self, key):
        if self.default_factory is None:
            raise KeyError(key)
        else:
            ret = self[key] = self.default_factory(name=key)
            return ret
def __update_mean(self, rc, mc):
        mean = 0.0
        for index_point in range(len(self.__data)):
            mean += rc[index_point] * self.__data[index_point]