input: Write a python function to create a chatbot that responds to appointment booking requests and provides random responses for other messages.
  assert bot_responses('I want to book an appointment') == 'OK, please provide the following details: date, time, name, and the doctor you would like to visit.'
  assert bot_responses('My name is John, I want to book an appointment with Dr. Smith on 12th Dec at 10 AM') == 'Your appointment has been booked. Please arrive 15 minutes before your appointment time.'
  assert bot_responses('Hello') in ['I\'m sorry, I don\'t understand.','Can you please rephrase that?','What do you mean?']
output: import random
  
  def bot_responses(message):
      booking_keywords = ['book an appointment', 'schedule an appointment', 'make an appointment']
      if any(keyword in message.lower() for keyword in booking_keywords):
          if 'date' in message.lower() and 'time' in message.lower() and 'name' in message.lower() and 'doctor' in message.lower():
              return 'Your appointment has been booked. Please arrive 15 minutes before your appointment time.'
          else:
              return 'OK, please provide the following details: date, time, name, and the doctor you would like to visit.'
      else:
          random_responses = [
              "I'm sorry, I don't understand.",
              "Can you please rephrase that?",
              "What do you mean?"
          ]
          return random.choice(random_responses)