How to set slot value for form validation

Hi Team, i am struggling how to set extras slot value for form validation, i have extras slot name “rephrase”, want to set value for this slit my overall idea, i only want validate 2 times, after that it will stop asking form value again, please help me

def validate_tech_keyword(
    value: Text,
    dispatcher: CollectingDispatcher,
    tracker: Tracker,
    domain: Dict[Text, Any],
) -> Dict[Text, Any]:
    """Validate tech_keyword value."""
    rephrase = tracker.get_slot('rephrase')
    print("rephrase status " + str(rephrase))

    if response.text == "[]":
        if(rephrase == "askForRephrase"):
            dispatcher.utter_button_message("Sorry! cannot find anything related to your request.", buttons)
            # validation failed, set this slot to None, meaning the # user will be asked for the slot again
            dispatcher.utter_message("Sorry! We cannot find anything related to your request. Can you type a different keyword instead ?")
            return [SlotSet("rephrase", "askForRephrase"),{"tech_keyword": None}]
        # validation succeeded, set the value of the "cuisine" slot to value
        return {"tech_keyword": value}

can some one help me :(, need me provide more information please let me know