@Override
    public Void visit(FactoryExpression<?> expr, Void context) {
        handle(", ", expr.getArgs());
        return null;
    }
Generate a constant value under which to register a new constant in {@link #getConstantToLabel()}.

@param value the constant value or parameter to create a constant for
@return the generated label
querydsl-core/src/main/java/com/querydsl/core/support/SerializerBase.java