code: def yield_from_handle(self, tokens):
          
          internal_assert(len(tokens) == 1, "invalid yield from tokens", tokens)
          if self.target_info < (3, 3):
              return (
                  yield_from_var + " = " + tokens[0]
                  + "\nfor " + yield_item_var + " in " + yield_from_var + ":\n"
                  + openindent + "yield " + yield_item_var + "\n" + closeindent
              )
          else:
              return "yield from " + tokens[0]
docs: Process Python 3.3 yield from.