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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 get_resource(url):
 """ Issue a GET request to R25 with the given url and return a response as an etree element. """

    response = R25_DAO().getURL(url, {"Accept": "text/xml"})
    if response.status != 200:
        raise DataFailureException(url, response.status, response.data)

    tree = etree.fromstring(response.data.strip())

    # XHTML response is an error response
    xhtml = tree.xpath("//xhtml:html", namespaces=nsmap)
    if len(xhtml):
        raise DataFailureException(url, 500, response.data)

    return tree