public Optional<String> groupInstanceId() {
            return groupInstanceId;
        }
Unique name for this assignor (e.g. "range" or "roundrobin" or "sticky"). Note, this is not required
to be the same as the class name specified in {@link ConsumerConfig#PARTITION_ASSIGNMENT_STRATEGY_CONFIG}
@return non-null unique name
clients/src/main/java/org/apache/kafka/clients/consumer/ConsumerPartitionAssignor.java