input: Write a python function to handle a user registration process in Django.
  assert register_view('POST')== "Redirection to index"
  assert register_view('GET')== "Render registration form"
output: def register_view(request_method):
      if request_method == 'POST':
          return "Redirection to index"
      elif request_method == 'GET':
          return "Render registration form"
      else:
          return "Invalid request method"