private boolean offeredNodeHasParentHostnameAlreadyAccepted(NodeCandidate candidate) {
        if (candidate.parentHostname().isEmpty()) return false;
        return nodes.values().stream().anyMatch(acceptedNode -> acceptedNode.parentHostname().equals(candidate.parentHostname()));
    }
Returns the cause of retirement for given candidate
node-repository/src/main/java/com/yahoo/vespa/hosted/provision/provisioning/NodeAllocation.java