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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 extract_auth_vars(request):
 """ raven-js will pass both Authorization and X-Sentry-Auth depending on the browser and server configurations. """

    if request.META.get('HTTP_X_SENTRY_AUTH', '').startswith('Sentry'):
        return request.META['HTTP_X_SENTRY_AUTH']
    elif request.META.get('HTTP_AUTHORIZATION', '').startswith('Sentry'):
        return request.META['HTTP_AUTHORIZATION']
    else:
        # Try to construct from GET request
        args = [
            '%s=%s' % i
            for i in request.GET.items()
            if i[0].startswith('sentry_') and i[0] != 'sentry_data'
        ]
        if args:
            return 'Sentry %s' % ', '.join(args)
    return None