@Override
    public Predicate not() {
        if (not == null) {
            not = ExpressionUtils.predicate(Ops.NOT, this);
        }
        return not;
    }
{@code PredicateTemplate} provides a Boolean typed {@link TemplateExpression} implementation

@author tiwe
querydsl-core/src/main/java/com/querydsl/core/types/PredicateTemplate.java