private void throwIfNoAssignorsConfigured() {
        if (assignors.isEmpty())
            throw new IllegalStateException("Must configure at least one partition assigner class name to " +
                    ConsumerConfig.PARTITION_ASSIGNMENT_STRATEGY_CONFIG + " configuration property");
    }
Release the light lock protecting the consumer from multi-threaded access.
clients/src/main/java/org/apache/kafka/clients/consumer/internals/ClassicKafkaConsumer.java