input: Write a function that implements a basic chatbot in Python for responding to casual inquiries. The function should take a user input as its parameter, randomly select a response from a predefined list of possible answers, and return that response. If the user input is "Goodbye", the chatbot should terminate the conversation with a farewell message. The function should be named "chatbot_response".
  assert chatbot_response("How are you?")=="That's a great question!" or "I'm not sure, but I'll try to find out!" or "That sounds interesting, tell me more!" or "I have no idea, sorry!"
  assert chatbot_response("Tell me a joke")=="That's a great question!" or "I'm not sure, but I'll try to find out!" or "That sounds interesting, tell me more!" or "I have no idea, sorry!"
  assert chatbot_response("Goodbye")==None
output: import random
  
  def chatbot_response(user_input):
      responses = ["That's a great question!", "I'm not sure, but I'll try to find out!", "That sounds interesting, tell me more!", "I have no idea, sorry!"]
      if user_input == "Goodbye":
          return None
      return random.choice(responses)