def upgrade_languages(root, data):
langs = XPath('./opf:metadata/dc:language')(root)
if langs:
for lang in langs:
lang.attrib.clear()
else:
# EPUB spec says dc:language is required
metadata = XPath('./opf:metadata')(root)[0]
l = metadata.makeelement(DC('language'))
l.text = 'und'
metadata.append(l)
def remove_invalid_attrs_in_dc_metadata(root, data):
for tag in XPath('//*[namespace-uri() = "{}"]'.format(DC('')[1:-1]))(root):
for k in tuple(tag.attrib):
if k != 'id':
del tag.attrib[k]
