code: def mark_rewrite(self, *names):
          
          already_imported = set(names).intersection(set(sys.modules))
          if already_imported:
              for name in already_imported:
                  if name not in self._rewritten_names:
                      self._warn_already_imported(name)
          self._must_rewrite.update(names)
docs: Mark import names as needing to be re-written.
  
          The named module or package as well as any nested modules will
          be re-written on import.