code: def last(self, db=_DefaultDB):
          '''
          Return the last key/value pair from the given db.
          '''
          self._acqXactForReading()
          try:
              with self.xact.cursor(db=db.db) as curs:
                  if not curs.last():
                      return None
                  return curs.key(), curs.value()
          finally:
              self._relXactForReading(f last(self, db=_DefaultDB):
          '''
          Return the last key/value pair from the given db.
          '''
          self._acqXactForReading()
          try:
              with self.xact.cursor(db=db.db) as curs:
                  if not curs.last():
                      return None
                  return curs.key(), curs.value()
          finally:
              self._relXactForReading()
docs: Return the last key/value pair from the given db.