input: Write a python function to simulate a simple HTTP server that serves different pages based on the URL path.
  assert get_response('/page1') == b'This is page 1'
  assert get_response('/page2') == b'This is page 2'
  assert get_response('/nonexistent') == 404
output: def get_response(path):
      if path == '/page1':
          return b'This is page 1'
      elif path == '/page2':
          return b'This is page 2'
      else:
          return 404