protected static final Map<ClickHouseOption, Serializable> mergeOptions(List<ClickHouseConfig> list) {
        if (list == null || list.isEmpty()) {
            return Collections.emptyMap();
        }

        Map<ClickHouseOption, Serializable> options = new HashMap<>();
        List<ClickHouseConfig> cl = new ArrayList<>(list.size());
        for (ClickHouseConfig c : list) {
            if (c != null) {
                boolean duplicated = false;
                for (ClickHouseConfig conf : cl) {
                    if (conf == c) {
                        duplicated = true;
                        break;
                    }
                }

                if (duplicated) {
                    continue;
                }
                options.putAll(c.options);
                cl.add(c);
            }
        }

        return options;
    }
An immutable class holding client-specific options like
{@link ClickHouseCredentials} and {@link ClickHouseNodeSelector} etc.
clickhouse-client/src/main/java/com/clickhouse/client/ClickHouseConfig.java