@property
    def idx(self):
        filename = self.filename
        if not filename:
            return None
        name_part = posixpath.splitext(filename)[0]  # filename w/ext removed
        match = self._filename_re.match(name_part)
        if match is None:
            return None
        if match.group(2):
            return int(match.group(2))
        return None
Return partname index as integer for tuple partname or None for
dataset/ETHPy150Open python-openxml/python-docx/docx/opc/packuri.py/PackURI.idx