Return a flat list of sections (wo/section names) with GO terms grouped and sorted.

def get_sorted_nts_omit_section(self, hdrgo_prt, hdrgo_sort):
        """Return a flat list of sections (wo/section names) with GO terms grouped and sorted."""
        nts_flat = []
        # print("SSSS SorterNts:get_sorted_nts_omit_section(hdrgo_prt={}, hdrgo_sort={})".format(
        #     hdrgo_prt, hdrgo_sort))
        hdrgos_seen = set()
        hdrgos_actual = self.sortgos.grprobj.get_hdrgos()
        for _, section_hdrgos_all in self.sections:
            #section_hdrgos_act = set(section_hdrgos_all).intersection(hdrgos_actual)
            section_hdrgos_act = [h for h in section_hdrgos_all if h in hdrgos_actual]
            hdrgos_seen |= set(section_hdrgos_act)
            self.sortgos.get_sorted_hdrgo2usrgos(
                section_hdrgos_act, nts_flat, hdrgo_prt, hdrgo_sort)
        remaining_hdrgos = set(self.sortgos.grprobj.get_hdrgos()).difference(hdrgos_seen)
        self.sortgos.get_sorted_hdrgo2usrgos(remaining_hdrgos, nts_flat, hdrgo_prt, hdrgo_sort)
        return nts_flat