code: def decr(self, key, value, noreply=False):
          
          key = self.check_key(key)
          cmd = b'decr ' + key + b' ' + six.text_type(value).encode('ascii')
          if noreply:
              cmd += b' noreply'
          cmd += b'\r\n'
          results = self._misc_cmd([cmd], b'decr', noreply)
          if noreply:
              return None
          if results[0] == b'NOT_FOUND':
              return None
          return int(results[0])
docs: The memcached "decr" command.
  
          Args:
            key: str, see class docs for details.
            value: int, the amount by which to increment the value.
            noreply: optional bool, False to wait for the reply (the default).
  
          Returns:
            If noreply is True, always returns None. Otherwise returns the new
            value of the key, or None if the key wasn't found.