'Duplicate data so that any changes we make to markup/CSS only
affect KF8 output and not MOBI 6 output'

def dup_data(self):

    self._data_cache = {}
    cssutils.log.setLevel(logging.CRITICAL)
    for item in self.oeb.manifest:
        if (item.media_type in XML_DOCS):
            self._data_cache[item.href] = copy.deepcopy(item.data)
        elif (item.media_type in OEB_STYLES):
            self._data_cache[item.href] = cssutils.parseString(item.data.cssText, validate=False)
