How to use the hachoir.field.NullBytes function in hachoir

def createFields(self):
        if self.stream.readBytes(self.absolute_address, 5) != b"Adobe":
            yield RawBytes(self, "raw", self.size // 8, "Raw data")
            return
        yield String(self, "adobe", 5, "\"Adobe\" string", charset="ASCII")
        yield UInt16(self, "version", "DCT encoder version")
        yield Enum(Bit(self, "flag00"),
                   {False: "Chop down or subsampling", True: "Blend"})
        yield NullBits(self, "flags0_reserved", 15)
        yield NullBytes(self, "flags1", 2)
        yield Enum(UInt8(self, "color_transform", "Colorspace transformation code"), self.COLORSPACE_TRANSFORMATION)

yield String(self, "name", 100, "Name", strip="\0", charset="ISO-8859-1")
        yield String(self, "mode", 8, "Mode", strip=" \0", charset="ASCII")
        yield String(self, "uid", 8, "User ID", strip=" \0", charset="ASCII")
        yield String(self, "gid", 8, "Group ID", strip=" \0", charset="ASCII")
        yield String(self, "size", 12, "Size", strip=" \0", charset="ASCII")
        yield String(self, "mtime", 12, "Modification time", strip=" \0", charset="ASCII")
        yield String(self, "check_sum", 8, "Check sum", strip=" \0", charset="ASCII")
        yield Enum(UInt8(self, "type", "Type"), self.type_name)
        yield String(self, "lname", 100, "Link name", strip=" \0", charset="ISO-8859-1")
        yield String(self, "magic", 8, "Magic", strip=" \0", charset="ASCII")
        yield String(self, "uname", 32, "User name", strip=" \0", charset="ISO-8859-1")
        yield String(self, "gname", 32, "Group name", strip=" \0", charset="ISO-8859-1")
        yield String(self, "devmajor", 8, "Dev major", strip=" \0", charset="ASCII")
        yield String(self, "devminor", 8, "Dev minor", strip=" \0", charset="ASCII")
        yield String(self, "prefix", 155, "Prefix for filename", strip="\0", charset="ASCII")
        yield NullBytes(self, "padding", 12, "Padding (zero)")

        filesize = self.getOctal("size")
        if filesize:
            yield SubFile(self, "content", filesize, filename=self["name"].value)

        size = paddingSize(self.current_size // 8, 512)
        if size:
            yield NullBytes(self, "padding_end", size, "Padding (512 align)")

if size:
            if self["type"].value == self.TYPE_STRING:
                if self.is_32bit:
                    size *= 2
                yield String(self, "value", size, charset="UTF-16-LE", truncate="\0")
            elif self["name"].value == "VS_VERSION_INFO":
                yield VersionInfoBinary(self, "value", size=size * 8)
                if self["value/file_flags_mask"].value == 0:
                    self.is_32bit = False
            else:
                yield RawBytes(self, "value", size)
        while 12 <= (self.size - self.current_size) // 8:
            yield VersionInfoNode(self, "node[]", self.is_32bit)
        size = (self.size - self.current_size) // 8
        if size:
            yield NullBytes(self, "padding[]", size)

raise ParserError("OLE2: Too much sections (%s)" %
                              self["section_count"].value)

        section_indexes = []
        for index in range(self["section_count"].value):
            section_index = SummaryIndex(self, "section_index[]")
            yield section_index
            section_indexes.append(section_index)

        for section_index in section_indexes:
            self.seekByte(section_index["offset"].value)
            yield SummarySection(self, "section[]")

        size = (self.size - self.current_size) // 8
        if 0 < size:
            yield NullBytes(self, "end_padding", size)

def createFields(self):
        LONG = Int32
        yield UInt32(self, "type", "Record type (always 1)")
        yield UInt32(self, "size", "Size of the header in bytes")
        yield RECT32(self, "Bounds", "Inclusive bounds")
        yield RECT32(self, "Frame", "Inclusive picture frame")
        yield textHandler(UInt32(self, "signature", "Signature ID (always 0x464D4520)"), hexadecimal)
        yield UInt16(self, "min_ver", "Minor version")
        yield UInt16(self, "maj_ver", "Major version")
        yield UInt32(self, "file_size", "Size of the file in bytes")
        yield UInt32(self, "NumOfRecords", "Number of records in the metafile")
        yield UInt16(self, "NumOfHandles", "Number of handles in the handle table")
        yield NullBytes(self, "reserved", 2)
        yield UInt32(self, "desc_size", "Size of description in 16-bit words")
        yield UInt32(self, "desc_ofst", "Offset of description string in metafile")
        yield UInt32(self, "nb_colors", "Number of color palette entries")
        yield LONG(self, "width_px", "Width of reference device in pixels")
        yield LONG(self, "height_px", "Height of reference device in pixels")
        yield LONG(self, "width_mm", "Width of reference device in millimeters")
        yield LONG(self, "height_mm", "Height of reference device in millimeters")

        # Read description (if any)
        offset = self["desc_ofst"].value
        current = (self.absolute_address + self.current_size) // 8
        size = self["desc_size"].value * 2
        if offset == current and size:
            yield String(self, "description", size, charset="UTF-16-LE", strip="\0 ")

        # Read padding (if any)

def createFields(self):
        yield RawBytes(self, "md5", 16)
        while True:
            size = (self.size - self.current_size) // 8
            if size < 77:
                break
            yield EncryptedItem(self, "item[]")
        size = paddingSize(self.current_size // 8, 16)
        if size:
            yield NullBytes(self, "padding_align", size)

yield Bit(self, "last_metadata_block", "True if this is the last metadata block")
        yield Enum(Bits(self, "block_type", 7, "Metadata block header type"), self.BLOCK_TYPE_DESC)
        yield UInt24(self, "metadata_length", "Length of following metadata in bytes (doesn't include this header)")

        block_type = self["block_type"].value
        size = self["metadata_length"].value
        if not size:
            return
        try:
            handler = self.BLOCK_TYPES[block_type][2]
        except KeyError:
            handler = None
        if handler:
            yield handler(self, "content", size=size * 8)
        elif self["block_type"].value == 1:
            yield NullBytes(self, "padding", size)
        else:
            yield RawBytes(self, "rawdata", size)

def createFields(self):
        yield GUID(self, "clsid", "16 bytes GUID used by some apps")
        yield UInt16(self, "ver_min", "Minor version")
        yield UInt16(self, "ver_maj", "Major version")
        yield Bytes(self, "endian", 2, "Endian (\\xfe\\xff for little endian)")
        yield UInt16(self, "bb_shift", "Log, base 2, of the big block size")
        yield UInt16(self, "sb_shift", "Log, base 2, of the small block size")
        yield NullBytes(self, "reserved[]", 6, "(reserved)")
        yield UInt32(self, "csectdir", "Number of SECTs in directory chain for 4 KB sectors (version 4)")
        yield UInt32(self, "bb_count", "Number of Big Block Depot blocks")
        yield SECT(self, "bb_start", "Root start block")
        yield NullBytes(self, "transaction", 4, "Signature used for transactions (must be zero)")
        yield UInt32(self, "threshold", "Maximum size for a mini stream (typically 4096 bytes)")
        yield SECT(self, "sb_start", "Small Block Depot start block")
        yield UInt32(self, "sb_count")
        yield SECT(self, "db_start", "First block of DIFAT")
        yield UInt32(self, "db_count", "Number of SECTs in DIFAT")

def createFields(self):
        if False:
            yield UInt32(self, "width0")
            yield UInt32(self, "height0")
            yield PaddingBytes(self, "reserved[]", 7)
            yield UInt32(self, "width")
            yield UInt32(self, "height")
            yield PaddingBytes(self, "reserved[]", 2)
            yield UInt16(self, "depth")
            yield Enum(String(self, "codec", 4, charset="ASCII"), video_fourcc_name)
            yield NullBytes(self, "padding", 20)
        else:
            yield UInt32(self, "width")
            yield UInt32(self, "height")
            yield PaddingBytes(self, "reserved[]", 1)
            yield UInt16(self, "format_data_size")
            if self["format_data_size"].value < 40:
                raise ParserError("Unknown format data size")
            yield BitmapInfoHeader(self, "bmp_info", use_fourcc=True)

def createFields(self):
        yield textHandler(UInt32(self, "signature", "Placeable Metafiles signature (0x9AC6CDD7)"), hexadecimal)
        yield UInt16(self, "handle")
        yield RECT16(self, "rect")
        yield UInt16(self, "inch")
        yield NullBytes(self, "reserved", 4)
        yield textHandler(UInt16(self, "checksum"), hexadecimal)