How to use the tifffile.TiffTag function in tifffile

def _process_tags(self):
        """Validate standard tags and initialize attributes.

        Raise ValueError if tag values are not supported.

        """
        tags = self.tags
        for code, (name, default, dtype, count, validate) in TIFF_TAGS.items():
            if not (name in tags or default is None):
                tags[name] = TiffTag(code, dtype=dtype, count=count,
                                     value=default, name=name)
            if name in tags and validate:
                try:
                    if tags[name].count == 1:
                        setattr(self, name, validate[tags[name].value])
                    else:
                        setattr(self, name, tuple(
                            validate[value] for value in tags[name].value))
                except KeyError:
                    raise ValueError("%s.value (%s) not supported" %
                                     (name, tags[name].value))

        tag = tags['bits_per_sample']
        if tag.count == 1:
            self.bits_per_sample = tag.value
        else:

if not offset:
            raise StopIteration()

        # read standard tags
        tags = self.tags
        fh.seek(offset)
        fmt, size = {4: ('H', 2), 8: ('Q', 8)}[offset_size]
        try:
            numtags = struct.unpack(byteorder + fmt, fh.read(size))[0]
        except Exception:
            warnings.warn("corrupted page list")
            raise StopIteration()

        for _ in range(numtags):
            try:
                tag = TiffTag(self.parent)
                tags[tag.name] = tag
            except TiffTag.Error as e:
                warnings.warn(str(e))

        # read LSM info subrecords
        if self.is_lsm:
            pos = fh.tell()
            for name, reader in CZ_LSM_INFO_READERS.items():
                try:
                    offset = self.cz_lsm_info['offset_'+name]
                except KeyError:
                    continue
                if not offset:
                    continue
                fh.seek(offset)
                try: