code: public PropertiesProvider getProvider(String filename) {
      if (filename.endsWith(".yaml") || filename.endsWith(".yml")) {
        return yamlProvider;
      } else if (filename.endsWith(".json")) {
        return jsonProvider;
      } else {
        return propertiesProvider;
      }
    }
docs: Selects {@link PropertiesProvider} to use based on a file extension. For *.yaml files
  returns {@code yamlProvider}. For any other extension returns {@code propertiesProvider}.
  
  @param filename configuration file name
  @return provider for the give file type