@Override
    public String toString() {
        return "(" +
            "groupId='" + groupId + '\'' +
            ", isSimpleConsumerGroup=" + isSimpleConsumerGroup +
            ", state=" + state +
            ", type=" + type +
            ')';
    }
The type of the consumer group.

@return An Optional containing the type, if available.
clients/src/main/java/org/apache/kafka/clients/admin/ConsumerGroupListing.java