docs: public static ConfigSyntax syntaxFromExtension(String filename) {
          if (filename == null)
              return null;
          else if (filename.endsWith(".json"))
              return ConfigSyntax.JSON;
          else if (filename.endsWith(".conf"))
              return ConfigSyntax.CONF;
          else if (filename.endsWith(".properties"))
              return ConfigSyntax.PROPERTIES;
          else
              return null;
      }