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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 nrfa_metadata():
 """ Return metadata on the NRFA data. Returned metadata is a dict with the following elements: - `url`: string with NRFA data download URL - `version`: string with NRFA version number, e.g. '3.3.4' - `published_on`: datetime of data release/publication (only month and year are accurate, rest should be ignored) - `downloaded_on`: datetime of last download :return: metadata :rtype: dict """

    result = {
        'url': config.get('nrfa', 'url', fallback=None) or None,  # Empty strings '' become None
        'version': config.get('nrfa', 'version', fallback=None) or None,
        'published_on': config.get_datetime('nrfa', 'published_on', fallback=None) or None,
        'downloaded_on': config.get_datetime('nrfa', 'downloaded_on', fallback=None) or None
    }
    return result