Plot GO DAGs for groups of user GOs which are not in a section.

def plot_groups_unplaced(self, fout_dir=".", **kws_pltargs):
        """Plot GO DAGs for groups of user GOs which are not in a section."""
        hdrgos = self.grprobj.get_hdrgos_unplaced()
        pltargs = PltGroupedGosArgs(self.grprobj, fout_dir=fout_dir, **kws_pltargs)
        return self._plot_groups_hdrgos(hdrgos, pltargs)