Disconnect all slots, if any, connected to this signaler in the specified group. Any signal emitted on the corresponding signaler that happens after this call to disconnect completes will not call any slots in group that were connected prior to this call. Throws nothing. Note that this function does not block the calling thread pending completion of ongoing signals emitted on the signaler. Also note that it is unspecified how many affected slots, if any, will be signalled to by any invocation on the signaler that begins before this function completes. Also note that if a slot in group is connected to this signaler during a call to this function, it is unspecified whether that slot will be disconnected.