/// <summary>
 /// Returns a sequence of two table fields.
 /// </summary>
 public static IEnumerable <EwfTableField> Append(this EwfTableField first, EwfTableField second) =>
 Enumerable.Empty <EwfTableField>().Append(first).Append(second);
 /// <summary>
 /// Concatenates table fields.
 /// </summary>
 public static IEnumerable <EwfTableField> Concat(this EwfTableField first, IEnumerable <EwfTableField> second) => second.Prepend(first);