code: def _get_pltdag_ancesters(self, hdrgo, usrgos, desc=""):
          
          go_srcs = usrgos.union([hdrgo])
          gosubdag = GoSubDag(go_srcs,
                              self.gosubdag.get_go2obj(go_srcs),
                              relationships=self.gosubdag.relationships,
                              rcntobj=self.gosubdag.rcntobj,
                              go2nt=self.gosubdag.go2nt)
          tot_usrgos = len(set(gosubdag.go2obj.keys()).intersection(self.usrgos))
          return self.ntpltgo(
              hdrgo=hdrgo,
              gosubdag=gosubdag,
              tot_usrgos=tot_usrgos,
              parentcnt=False,
              desc=desc)
docs: Get GoSubDag containing hdrgo and all usrgos and their ancesters.