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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 static_url(context, static_file_path):
 """Filter for generating urls for static files. NOTE: you'll need to set app['static_root_url'] to be used as the root for the urls returned. Usage: {{ static('styles.css') }} might become "/static/styles.css" or "http://mycdn.example.com/styles.css" """

    app = context['app']
    try:
        static_url = app['static_root_url']
    except KeyError:
        raise RuntimeError(
            "app does not define a static root url "
            "'static_root_url', you need to set the url root "
            "with app['static_root_url'] = '<static root>'.") from None
    return '{}/{}'.format(static_url.rstrip('/'), static_file_path.lstrip('/'))