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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def begin(request, provider):
 """ Display authentication form. This is also the first step in registration. The actual login is in social_complete function below. """

    # store url to where user will be redirected
    request.session['next_url'] = request.GET.get("next") or settings.LOGIN_REDIRECT_URL

    # start the authentication process
    backend = get_backend(provider)
    return backend.begin(request, dict(request.REQUEST.items()))