superdiagonal_align = kRight;
      subdiagonal_align = kRight;
    } else if (align == "LEFT_RIGHT") {
      superdiagonal_align = kLeft;
      subdiagonal_align = kRight;
    } else if (align == "LEFT_LEFT") {
      superdiagonal_align = kLeft;
      subdiagonal_align = kLeft;
    } else {
      return failure();  // unsupported alignment
    }