'If there is a reference to the cover/titlepage via manifest properties, convert to
entries in the <guide> so that the rest of the pipeline picks it up.'

def rationalize_cover3(self, opf, log):

    from calibre.ebooks.metadata.opf3 import items_with_property
    removed = None
    raster_cover_href = opf.epub3_raster_cover
    if raster_cover_href:
        self.set_guide_type(opf, 'cover', raster_cover_href, 'Cover    Image')
    titlepage_id = titlepage_href = None
    for item in items_with_property(opf.root, 'calibre:title-page'):
        (tid, href) = (item.get('id'), item.get('href'))
        if (href and tid):
            (titlepage_id, titlepage_href) = (tid, href.partition('#')[0])
            break
    if (titlepage_href is not None):
        self.set_guide_type(opf, 'titlepage', titlepage_href, 'Title    Page')
        spine = list(opf.iterspine())
        if (len(spine) > 1):
            for item in spine:
                if (item.get('idref') == titlepage_id):
                    log('Found    HTML    cover', titlepage_href)
                    if self.for_viewer:
                        item.attrib.pop('linear', None)
                    else:
                        item.getparent().remove(item)
                        removed = titlepage_href
                    return removed
