valsource=message.getOrNull(MessageSource)?:error("Cannot find MessageSource from message")
check(sourceisOnlineMessageSource.Incoming.FromFriend){"source provided to a FriendMessage must be an instance of OnlineMessageSource.Incoming.FromFriend"}
valsource=message.getOrNull(MessageSource)?:error("Cannot find MessageSource from message")
check(sourceisOnlineMessageSource.Incoming.FromGroup){"source provided to a GroupMessage must be an instance of OnlineMessageSource.Incoming.FromGroup"}