Creating a 'holdable button' with gpiozero

holdbutton.py

from gpiozero import Button
from threading import Timer

class HoldableButton(Button):
    def __init__(self, pin=None, pull_up=True, bounce_time=None, hold_time=1, repeat=False): 

        super(HoldableButton, self).__init__(pin, pull_up, bounce_time)

        # Set Button when_pressed and when_released to call local functions
        # cant use super() as it doesn't support setters
        Button.when_pressed.fset(self, self._when_button_pressed)
        Button.when_released.fset(self, self._when_button_released)

        self._when_held = None
        self._when_pressed = None
        self._when_released = None
        self._is_held = False

        self.hold_time = hold_time
        self.repeat = repeat
        self._held_timer = None

    #override button when_pressed and when_released
    @property
    def when_pressed(self):
        return self._when_pressed

    @when_pressed.setter
    def when_pressed(self, value):
        self._when_pressed = value

    @property
    def when_released(self):
        return self._when_released

    @when_released.setter
    def when_released(self, value):
        self._when_released = value

    @property
    def when_held(self):
        return self._when_held

    @when_held.setter
    def when_held(self, value):
        self._when_held = value

    @property
    def is_held(self):
        return self._is_held

    def _when_button_pressed(self):
        self._start_hold()
        if self._when_pressed != None:
            self._when_pressed()

    def _when_button_released(self):
        self._is_held = False
        self._stop_hold()
        if self._when_released != None:
            self.when_released()

    def _start_hold(self):
        self._held_timer = Timer(self.hold_time, self._button_held)
        self._held_timer.start()

    def _stop_hold(self):
        if self._held_timer != None:
            self._held_timer.cancel()

    def _button_held(self):
        self._is_held = True
        if self._when_held != None:
            if self.repeat and self.is_pressed:
                self._start_hold()
            self._when_held()
        
if __name__ == "__main__":
    from time import sleep
    def button_pressed():
        print("pressed")
    def button_released():
        print("released")
    def button_held():
        print("held")
    pin = 26
    but = HoldableButton(pin, hold_time = 0.5, repeat = True)    
    but.when_held = button_held
    but.when_pressed = button_pressed
    but.when_released = button_released
    while True:
        sleep(0.1)
        print("Is held = {}".format(but.is_held))