text: import RPi.GPIO as GPIO
  import pyrebase
  
  PATH_LISTENING = '/GPIO_05'
  GPIO_OUTPUT = 5
  # config of Firebase
  config = {
    "apiKey": "---------",
    "authDomain": "???.firebaseapp.com",
    "databaseURL": "https://???.firebaseio.com",
    "storageBucket": "???.appspot.com"
  }
  
  # use the position on board as it's name
  GPIO.setmode(GPIO.BOARD)
  
  # tell raspberry : this is an output.
  GPIO.setup(GPIO_OUTPUT,GPIO.OUT) 
  
  
  firebase = pyrebase.initialize_app(config)
  db = firebase.database()
  ''' use these to test:
  gpio = db.child("GPIO").get()
  print(gpio.val())
  '''
  
  def stream_handler(message):
      if message["data"]==True and message['path']==PATH_LISTENING:
          print ('ON!')
          GPIO.output(GPIO_OUTPUT, GPIO.HIGH)
      else:
          print ('Off...')
          GPIO.output(GPIO_OUTPUT, GPIO.LOW)
  
  my_stream = db.child("GPIO").stream(stream_handler)
  
  # my_stream.close() 
  