Return a pretty-printed XML string for the Element.

def prettify(elem):
    # from xml.etree.ElementTree import Element, SubElement, Comment, tostring
    from xml.etree import ElementTree
    from xml.dom import minidom
    """Return a pretty-printed XML string for the Element.
    """
    rough_string = ElementTree.tostring(elem, 'utf-8')
    reparsed = minidom.parseString(rough_string)
    return reparsed.toprettyxml(indent="  ")