Given namedtuples in each sectin, get counts of header GO IDs and sections.

def summarize_sec2hdrnts(self, sec2d_hdrnts):
        """Given namedtuples in each sectin, get counts of header GO IDs and sections."""
        sec2d_hdrgos = [(s, set(nt.GO for nt in nts)) for s, nts in sec2d_hdrnts]
        return self.summarize_sec2hdrgos(sec2d_hdrgos)