docs: def clear_doc(self, docname):
          """Remove the data associated with this instance of the domain."""
          for fullname, (fn, x) in self.data['objects'].items():
              if fn == docname:
                  del self.data['objects'][fullname]
          for modname, (fn, x, x, x) in self.data['modules'].items():
              if fn == docname:
                  del self.data['modules'][modname]
          for labelname, (fn, x, x) in self.data['labels'].items():
              if fn == docname:
                  del self.data['labels'][labelname]
          for anonlabelname, (fn, x) in self.data['anonlabels'].items():
              if fn == docname:
                  del self.data['anonlabels'][anonlabelname]