private boolean canTopicParticipateInReassignment(String topic) {
            // if a topic has two or more potential consumers it is subject to reassignment.
            return topic2AllPotentialConsumers.get(topic).size() >= 2;
        }
attempt to assign all unassigned partitions

@param unassignedPartitions partitions that are still unassigned
@param rackInfo             rack information used to match racks. If null, no rack-matching is performed
@param removeAssigned       flag that indicates if assigned partitions should be removed from `unassignedPartitions`
clients/src/main/java/org/apache/kafka/clients/consumer/internals/AbstractStickyAssignor.java