code: public static Config getFixedConfig(@Nullable final AbstractConfiguration ... configs)
      {
          final CombinedConfiguration cc = new CombinedConfiguration(new OverrideCombiner());
  
          if (configs != null) {
              for (final AbstractConfiguration config : configs) {
                  cc.addConfiguration(config);
              }
          }
          return new Config(cc);
      }
docs: Creates a fixed configuration for the supplied {@link AbstractConfiguration} objects. Only key/value
  pairs from these objects will be present in the final configuration.
  
  There is no implicit override from system properties.