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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 render_unregistered(error=None):
 """ Render template file for the unregistered user. Args: error (str, default None):
 Optional error message. Returns: str: Template filled with data. """

    return template(
        read_index_template(),
        registered=False,
        error=error,
        seeder_data=None,
        url_id=None,
    )