input: from typing import List, Dict
  
  def simple_chatbot():
      """Implement a simple chatbot using state diagrams. The chatbot transitions between different states based on user input and provides appropriate responses for each state. The state transitions are defined in a dictionary, and each state contains a message and possible replies. The chatbot keeps track of the conversation and ends when it reaches a terminal state.
  
      >>> chatbot_output = simple_chatbot()
      >>> 'Conversation:' in chatbot_output
      True
      """
      # State definitions are intentionally omitted for brevity.
      # They can be inserted into this function before the while loop.
      pass
output:     
      states = {
          'start': {
              'message': "Hello! How can I help you today?",
              'replies': {
                  '1': 'I need help with something.',
                  '2': 'I want to know more about your services.',
                  '3': 'I want to end the conversation.'
              },
              'next_state': {
                  '1': 'help',
                  '2': 'services',
                  '3': 'end'
              }
          },
          'help': {
              'message': "What do you need help with?",
              'replies': {
                  '1': 'I need technical support.',
                  '2': 'I need customer service.',
                  '3': 'Go back to the start.'
              },
              'next_state': {
                  '1': 'technical_support',
                  '2': 'customer_service',
                  '3': 'start'
              }
          },
          'services': {
              'message': "Here are our services:",
              'replies': {
                  '1': 'Tell me more about service 1.',
                  '2': 'Tell me more about service 2.',
                  '3': 'Go back to the start.'
              },
              'next_state': {
                  '1': 'service_1',
                  '2': 'service_2',
                  '3': 'start'
              }
          },
          'end': {
              'message': "Thank you for the conversation. Goodbye!",
              'replies': {},
              'next_state': {}
          }
      }
  
      current_state = 'start'
      conversation = []
  
      while current_state != 'end':
          state_info = states[current_state]
          conversation.append(state_info['message'])
          for key, reply in state_info['replies'].items():
              conversation.append(f"{key}: {reply}")
          user_input = input("Your choice: ")
          if user_input in state_info['next_state']:
              current_state = state_info['next_state'][user_input]
          else:
              conversation.append("Invalid choice. Please try again.")
  
      conversation.append(states['end']['message'])
      return "\n".join(["Conversation:"] + conversation)
  