code: def msetnx(self, key, value, *pairs):
          
          if len(pairs) % 2 != 0:
              raise TypeError("length of pairs must be even number")
          return self.execute(b'MSETNX', key, value, *pairs)
docs: Set multiple keys to multiple values,
          only if none of the keys exist.
  
          :raises TypeError: if len of pairs is not event number