input: Write a function to implement a chatbot in Python that can provide customer support in a restaurant based on a user's input from a file named 'random_user_question.txt'. The function should read the user's question, choose a random response from a predefined list of possible answers, and display the response to the user. If the file 'random_user_question.txt' is empty, the function should return a default response indicating that no question was asked.
  def restaurant_chatbot():
      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?'
      ]
      
      try:
          with open('random_user_question.txt') as user_question:
              question = user_question.read()
              if not question:
                  return 'No question was asked.'
              response = random.choice(possible_responses)
              return response
      except FileNotFoundError:
          return 'The file "random_user_question.txt" does not exist.'
  
  assert restaurant_chatbot()=='Check out our menu for a full list of options'
  assert restaurant_chatbot()=='We have a unique selection of meals - have you checked out our menu?'
  assert restaurant_chatbot()=='No question was asked.'
  assert restaurant_chatbot()=='We serve a variety of dishes, including traditional Italian, Mexican, and American fare. What would you like to try?'
  assert restaurant_chatbot()=='We have a great selection of meals! What kind of dish are you looking for?'
output: def restaurant_chatbot():
      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?'
      ]
      
      try:
          with open('random_user_question.txt') as user_question:
              question = user_question.read()
              if not question:
                  return 'No question was asked.'
              response = random.choice(possible_responses)
              return response
      except FileNotFoundError:
          return 'The file "random_user_question.txt" does not exist.'