code: def _check_feature_dependences(self):
          
          for mid in self.modules:
              for fst in self.modules[mid].statement.find_all("feature"):
                  fn, fid = self.resolve_pname(fst.argument, mid)
                  if fn not in self.modules[fid].features:
                      continue
                  if not self.if_features(fst, mid):
                      raise FeaturePrerequisiteError(*fn)
docs: Verify feature dependences.