public static void checkTypeMatch(SelTypes lhs, SelTypes rhs) {
    if (lhs != rhs) {
      throw new IllegalArgumentException(
          "Type mismatch, lhs type: " + lhs + ", rhs object type: " + rhs);
    }
  }
@Test
  public void testTypeMatch() {
    SelTypeUtil.checkTypeMatch(SelTypes.NULL, SelTypes.NULL);
  }