public Map<String, TopicCreationGroup> topicGroups() {
        return topicGroups;
    }
Return the topic creation groups defined for a source connector as a map of topic creation
group name to topic creation group instance. This map maintains all the optionally defined
groups besides the default group which is defined for any connector when topic creation is
enabled.

@return the map of all the topic creation groups besides the default group; may be empty
but not {@code null}
connect/runtime/src/main/java/org/apache/kafka/connect/util/TopicCreation.java