         }
         else {
             // log message if the user is mutually excluded
-            logger?.log(level: .error, message: String(format:"User not bucketed into variation. Mutually excluded via group %@", group?.id ?? "unknown"))
+            logger?.log(level: .error, message: "User not bucketed into variation. Mutually excluded via group \(group?.id ?? "unknown")")
 
             return nil;
         }

        }
        
        // log error if invalid bucketing id
        logger?.log(level: .error, message: String(format:"Invalid bucketing value for experiment %@", experiment.key))

        return nil;


        
        if experiment.trafficAllocation.count == 0 {
            // log error if there are no traffic allocation values
            logger?.log(level: .error, message: "Experiment \(experiment.key) has no traffic allocation")

            return nil
        }
