get the omitted jco

        Returns
        -------
        omitted_jco : pyemu.Jco

        Note
        ----
        returns a reference
        
        if ErrorVariance.__omitted_jco is None,
        then dynamically load the attribute before returning

def omitted_jco(self):
        """get the omitted jco

        Returns
        -------
        omitted_jco : pyemu.Jco

        Note
        ----
        returns a reference
        
        if ErrorVariance.__omitted_jco is None,
        then dynamically load the attribute before returning
        
        """
        if self.__omitted_jco is None:
            self.log("loading omitted_jco")
            self.__load_omitted_jco()
            self.log("loading omitted_jco")
        return self.__omitted_jco