private static <F extends Field> F parse(FieldParser parser,
String fieldName, String fieldBody) {
String rawStr = MimeUtil.fold(fieldName + ": " + fieldBody, 0);
ByteSequence raw = ContentUtil.encode(rawStr);
Field field = parser.parse(fieldName, fieldBody, raw);
@SuppressWarnings("unchecked")
F f = (F) field;
return f;
}