@Override
    public void close(String node) {
        connections.remove(node);
    }
Raise an unsupported version error on the next request if it matches the given matcher.
If the matcher does not match, {@link KafkaClient#send(ClientRequest, long)} will throw IllegalStateException.
@param matcher The request matcher to apply
clients/src/test/java/org/apache/kafka/clients/MockClient.java