private Map<String, String> mapWithPrefix(String prefix, ConfigKey key, Properties properties) {
   return extractFromPropertiesAsMap(key.asPropertyKey(prefix), properties);
 }
 private String withPrefix(String prefix, ConfigKey key, Properties properties) {
   return properties.getProperty(key.asPropertyKey(prefix));
 }
 private List<String> listWithPrefix(String prefix, ConfigKey key, Properties properties) {
   return extractFromPropertiesAsList(key.asPropertyKey(prefix), properties);
 }