code: def iter_symbols(code):
      
      for name in code.co_names:
          yield name
      for const in code.co_consts:
          if isinstance(const, six.string_types):
              yield const
          elif isinstance(const, CodeType):
              for name in iter_symbols(const):
                  yield name
docs: Yield names and strings used by `code` and its nested code objects