get the omitted prediction sensitivity vectors (stored as
        a pyemu.Matrix)

        Returns
        -------
        omitted_predictions : pyemu.Matrix
            a matrix of prediction sensitivity vectors (column wise) to
            omitted parameters

        Note
        ----
        returns a reference
        
        if ErrorVariance.__omitted_predictions is not set, then dynamically load the
        attribute before returning

def omitted_predictions(self):
        """ get the omitted prediction sensitivity vectors (stored as
        a pyemu.Matrix)

        Returns
        -------
        omitted_predictions : pyemu.Matrix
            a matrix of prediction sensitivity vectors (column wise) to
            omitted parameters

        Note
        ----
        returns a reference
        
        if ErrorVariance.__omitted_predictions is not set, then dynamically load the
        attribute before returning

        """
        if self.__omitted_predictions is None:
            self.log("loading omitted_predictions")
            self.__load_omitted_predictions()
            self.log("loading omitted_predictions")
        return self.__omitted_predictions