Available since: 2.0.0
Time complexity: O(N+M) where N is the number of patterns the client is already subscribed and M is the number of total patterns subscribed in the system (by any client).
Unsubscribes the client from the given patterns, or from all of them if none is given.
When no patterns are specified, the client is unsubscribed from all the previously subscribed patterns. In this case, a message for every unsubscribed pattern will be sent to the client.