Get placed/unplaced GO IDs and sections.

def get_summary_data(self, sec2d_nt):
        """Get placed/unplaced GO IDs and sections."""
        grouped = set()
        ungrouped = set()
        sections = set()
        secdflt = self.grprobj.hdrobj.secdflt
        for section_name, nts in sec2d_nt:
            if section_name != secdflt:
                if nts:
                    grouped.update(set(nt.GO for nt in nts))
                    sections.add(section_name)
                else:
                    ungrouped.update(set(nt.GO for nt in nts))
        return {'grouped':grouped, 'ungrouped':ungrouped, 'sections':sections}