docs: private static Selector simplifyNE(Selector sel0, Selector sel1) {
      if (sel0.getType() == Selector.BOOLEAN)
        return makeOR(makeAND(simplifyTree(sel0), simplifyNOT(sel1)),
                      makeAND(simplifyNOT(sel0), simplifyTree(sel1)));
      else if (sel0.getType() == Selector.STRING || sel0.getType() == Selector.UNKNOWN)
        return new OperatorImpl(Selector.NE, sel0, sel1);
      else
        // Numeric: transform into a pair of inequalities
        return makeOR(new OperatorImpl(Selector.LT, sel0, sel1),
                      new OperatorImpl(Selector.GT, sel0, sel1));
    }