Print grouped and sorted GO IDs.

def prt_nts(self, desc2nts, prt=sys.stdout, prtfmt=None):
        """Print grouped and sorted GO IDs."""
        # deprecated
        # Set print format string
        if prtfmt is None:
            prtfmt = "{{hdr1usr01:2}} {FMT}\n".format(FMT=self.grprobj.gosubdag.prt_attr['fmt'])
        # 1-D: data to print is a flat list of namedtuples
        if 'flat' in desc2nts:
            prt_txt(prt, desc2nts['flat'], prtfmt=prtfmt)
        # 2-D: data to print is a list of [(section, nts), ...
        else:
            WrSectionsTxt.prt_sections(prt, desc2nts['sections'], prtfmt)