docs: public static <T> Reader<T> elem(
  		final String name,
  		final Reader<? extends T> reader
  	) {
  		requireNonNull(name);
  		requireNonNull(reader);
  
  		return elem(
  			v -> {
  				@SuppressWarnings("unchecked")
  				T value = v.length > 0 ? (T)v[0] : null;
  				return value;
  			},
  			name,
  			reader
  		);
  	}