input: Write a function to implement a restaurant chatbot in Python that can provide customer support by reading a user's question from a text file and responding with a random pre-defined message. If the input file is empty or does not exist, the function should return a default message saying "No question provided."
  
  def restaurant_chatbot():
      try:
          with open('random_user_question.txt') as user_question:
              question = user_question.read()
              if not question.strip():
                  return "No question provided."
      except FileNotFoundError:
          return "No question provided."
  
      possible_responses = [
          'We serve a variety of dishes - from salads to pizzas to steaks!',
          'Check out our menu for a full list of options',
          'We serve a variety of dishes, including traditional Italian, Mexican, and American fare. What would you like to try?',
          'We have a great selection of meals! What kind of dish are you looking for?',
          'We have a unique selection of meals - have you checked out our menu?'
      ]
  
      response = random.choice(possible_responses)
      return response
  
  assert restaurant_chatbot()=="We serve a variety of dishes - from salads to pizzas to steaks!" or restaurant_chatbot()=="Check out our menu for a full list of options" or restaurant_chatbot()=="We serve a variety of dishes, including traditional Italian, Mexican, and American fare. What would you like to try?" or restaurant_chatbot()=="We have a great selection of meals! What kind of dish are you looking for?" or restaurant_chatbot()=="We have a unique selection of meals - have you checked out our menu?"
  assert restaurant_chatbot()=="No question provided."
output: def restaurant_chatbot():
      try:
          with open('random_user_question.txt') as user_question:
              question = user_question.read()
              if not question.strip():
                  return "No question provided."
      except FileNotFoundError:
          return "No question provided."
  
      possible_responses = [
          'We serve a variety of dishes - from salads to pizzas to steaks!',
          'Check out our menu for a full list of options',
          'We serve a variety of dishes, including traditional Italian, Mexican, and American fare. What would you like to try?',
          'We have a great selection of meals! What kind of dish are you looking for?',
          'We have a unique selection of meals - have you checked out our menu?'
      ]
  
      response = random.choice(possible_responses)
      return response