code: @SuppressWarnings("unchecked")
    public static AppYaml parse(InputStream input) throws AppEngineException {
      try {
        // our needs are simple so just load using primitive objects
        Yaml yaml = new Yaml(new SafeConstructor());
        Map<String, ?> contents = (Map<String, ?>) yaml.load(input);
        return new AppYaml(contents);
      } catch (YAMLException ex) {
        throw new AppEngineException("Malformed 'app.yaml'.", ex);
      }
    }
docs: Parse an app.yaml file to an AppYaml object.
  
  @param input the input, typically the contents of an {@code app.yaml} file
  @throws AppEngineException if reading app.yaml fails while scanning such as due to malformed
  YAML