code: public R isLessThan(V upper) {
      return create(e -> Expressions.call(Operators.LESS_THAN, e, Expressions.literal(upper)));
    }
docs: ]
  Checks that attribute is less than (but not equal to) {@code upper}.
  <p>Use {@link #isAtMost(Comparable)} for less <i>or equal</i> comparison</p>