def msetnx(self, mapping: Mapping[AnyKeyT, EncodableT]) -> Awaitable:
        """
        Sets key/values based on a mapping if none of the keys are already set.
        Mapping is a dictionary of key/value pairs. Both keys and values
        should be strings or types that can be cast to a string via str().
        Returns a boolean indicating if the operation was successful.
        """
        items: List[EncodableT] = []
        for pair in mapping.items():
            items.extend(pair)
        return self.execute_command("MSETNX", *items)

        Sets key/values based on a mapping if none of the keys are already set.
        Mapping is a dictionary of key/value pairs. Both keys and values
        should be strings or types that can be cast to a string via str().
        Returns a boolean indicating if the operation was successful.
        
aioredis/client.py