def swap$\_$ends$($message: str$)->$ str:

$"""$Return a new string that is message with the first and last

characters swapped.

Precondition: len$($message$)>=2$

$>>>$ swap$\_$ends$(\text{'}$cat$\text{'})$

'tac'

$>>>$ swap$\_$ends$(\text{'}$breakfast for dinner!$\text{'})$

$\text{'}!$reakfast for dinnerb'

$"""$

return last$\_$char $+$ middle $+$ first$\_$char