How to multicast message ?

[codeilm]

1. Right now we have feature to unicast (i.e. sending message to a single specified client) with the help of server.send_message(client,message)
2. Right now we also have feature to broadcast(i.e. sending message to all client) with the help of server.send_message_to_all(message)

But, How to multicast message (i.e. Sending message to multiple clients [not all clients]) ?

could you provider something like this
server.multicast(clients_list,message)