input: Write a python function to initiate a chatbot with a given conversation and respond to user inputs.
  assert chatbot_response('Hello') == 'Hi there!'
  assert chatbot_response('What is your name?') == 'My name is Bot. Nice to meet you!'
output: def chatbot_response(user_input):
      responses = {
          'Hello': 'Hi there!',
          'What is your name?': 'My name is Bot. Nice to meet you!'
      }
      return responses.get(user_input, "I don't understand that.")