Return a Grouper object, given a list of GOEnrichmentRecord.

def get_sortobj(self, goea_results, **kws):
        """Return a Grouper object, given a list of GOEnrichmentRecord."""
        nts_goea = MgrNtGOEAs(goea_results).get_goea_nts_prt(**kws)
        goids = set(nt.GO for nt in nts_goea)
        go2nt = {nt.GO:nt for nt in nts_goea}
        grprobj = Grouper("GOEA", goids, self.hdrobj, self.grprdflt.gosubdag, go2nt=go2nt)
        grprobj.prt_summary(sys.stdout)
        # hdrgo_prt", "section_prt", "top_n", "use_sections"
        sortobj = Sorter(grprobj, section_sortby=lambda nt: getattr(nt, self.pval_fld))
        return sortobj