input: Write a python function to toggle LED state using a given state parameter.
  assert LED_toggle("on") == GPIO.output(4,1)
  assert LED_toggle("off") == GPIO.output(4,0)
  assert LED_toggle("ON") == GPIO.output(4,1)
  assert LED_toggle("OFF") == GPIO.output(4,0)
output: def LED_toggle(state):
      import RPi.GPIO as GPIO
      GPIO.setmode(GPIO.BCM)
      GPIO.setup(4, GPIO.OUT)
      
      if state.lower() == "on":
          return GPIO.output(4, 1)
      elif state.lower() == "off":
          return GPIO.output(4, 0)
      else:
          raise ValueError("Invalid state. Use 'on' or 'off'.")