Stands for "qualified name", a utility function to turn a namespace
    prefixed tag name into a Clark-notation qualified tag name for lxml. For
    example, ``qn('p:cSld')`` returns ``'{http://schemas.../main}cSld'``.

def qn(tag):
    """
    Stands for "qualified name", a utility function to turn a namespace
    prefixed tag name into a Clark-notation qualified tag name for lxml. For
    example, ``qn('p:cSld')`` returns ``'{http://schemas.../main}cSld'``.
    """
    prefix, tagroot = tag.split(':')
    uri = nsmap[prefix]
    return '{%s}%s' % (uri, tagroot)