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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 create_free_space_request_content():
 """Creates an XML for requesting of free space on remote WebDAV server. :return: the XML string of request content. """

        root = etree.Element('propfind', xmlns='DAV:')
        prop = etree.SubElement(root, 'prop')
        etree.SubElement(prop, 'quota-available-bytes')
        etree.SubElement(prop, 'quota-used-bytes')
        tree = etree.ElementTree(root)
        return WebDavXmlUtils.etree_to_string(tree)