public function setControlSequenceIntroducer($controlSequenceIntroducer)
    {
        // Make sure it's a ControlFunction instance
        if (is_string($controlSequenceIntroducer)) {
            $controlSequenceIntroducer = new ControlFunction($controlSequenceIntroducer);
        }

        // @TODO: Check Validity
        $this->controlSequenceIntroducer = $controlSequenceIntroducer;

        return $this;
    }