code: def renamenx(self, key, newkey):
          
          if key == newkey:
              raise ValueError("key and newkey are the same")
          fut = self.execute(b'RENAMENX', key, newkey)
          return wait_convert(fut, bool)
docs: Renames key to newkey only if newkey does not exist.
  
          :raises ValueError: if key == newkey