get the names of the observations that
        are listed as less than inequality constraints.  Zero-
        weighted obs are skipped

        Returns
        -------
        pandas.Series : obsnme of obseravtions that are non-zero weighted
                        less than constraints

def less_than_obs_constraints(self):
        """get the names of the observations that
        are listed as less than inequality constraints.  Zero-
        weighted obs are skipped

        Returns
        -------
        pandas.Series : obsnme of obseravtions that are non-zero weighted
                        less than constraints

        """


        obs = self.observation_data
        lt_obs = obs.loc[obs.apply(lambda x: self._is_less_const(x.obgnme) \
                                             and x.weight != 0.0,axis=1),"obsnme"]
        return lt_obs