code: def find_unresolved_and_unreferenced_symbols(self):
          
          unresolved = set()
          unreferenced = self._definitions.copy()
          self._collect_unresolved_and_unreferenced(set(), set(), unresolved, unreferenced,
                                                    frozenset(self._definitions), start=True)
          return unresolved, unreferenced - Scope.ALL_BUILTINS
docs: Find any unresolved symbols, and unreferenced symbols from this scope.
  
          :returns: ({unresolved}, {unreferenced})