Can't initialize a SESBackend instance directly

You can get a `smtp.EmailBackend` instance by params without `settings.py`

    msg = EmailMultiAlternatives(...)
    connection = get_connection(backend="django.core.mail.backends.smtp.EmailBackend",
                                host=""
                                username=""....)
    msg.connection = connection
    msg.send(fail_silently=False)

But can't get a `SESBackend` instance without aws settings in `settings.py`, so I can't use different ses backend in my project which aws settings were saved in database.