How to use the dulwich.errors.ObjectFormatException function in dulwich

ObjectFormatException in case of parsing error (malformed
      field date)
    Returns: Tuple of (author, time, (timezone, timezone_neg_utc))
    """
    try:
        sep = value.rindex(b'> ')
    except ValueError:
        return (value, None, (None, False))
    try:
        person = value[0:sep+1]
        rest = value[sep+2:]
        timetext, timezonetext = rest.rsplit(b' ', 1)
        time = int(timetext)
        timezone, timezone_neg_utc = parse_timezone(timezonetext)
    except ValueError as e:
        raise ObjectFormatException(e)
    return person, time, (timezone, timezone_neg_utc)

:param text: Serialized text to parse
    :return: iterator of tuples of (name, mode, sha)
    :raise ObjectFormatException: if the object was malformed in some way
    """
    count = 0
    l = len(text)
    while count < l:
        mode_end = text.index(b' ', count)
        mode_text = text[count:mode_end]
        if strict and mode_text.startswith(b'0'):
            raise ObjectFormatException("Invalid mode '%s'" % mode_text)
        try:
            mode = int(mode_text, 8)
        except ValueError:
            raise ObjectFormatException("Invalid mode '%s'" % mode_text)
        name_end = text.index(b'\0', mode_end)
        name = text[mode_end+1:name_end]
        count = name_end+21
        sha = text[name_end+1:count]
        if len(sha) != 20:
            raise ObjectFormatException("Sha has invalid length")
        hexsha = sha_to_hex(sha)
        yield (name, mode, hexsha)

self._check_has_member("_commit_time", "missing commit time")

        for parent in self._parents:
            check_hexsha(parent, "invalid parent sha")
        check_hexsha(self._tree, "invalid tree sha")

        check_identity(self._author, "invalid author")
        check_identity(self._committer, "invalid committer")

        check_time(self._author_time)
        check_time(self._commit_time)

        last = None
        for field, _ in _parse_message(self._chunked_text):
            if field == _TREE_HEADER and last is not None:
                raise ObjectFormatException("unexpected tree")
            elif field == _PARENT_HEADER and last not in (_PARENT_HEADER,
                                                          _TREE_HEADER):
                raise ObjectFormatException("unexpected parent")
            elif field == _AUTHOR_HEADER and last not in (_TREE_HEADER,
                                                          _PARENT_HEADER):
                raise ObjectFormatException("unexpected author")
            elif field == _COMMITTER_HEADER and last != _AUTHOR_HEADER:
                raise ObjectFormatException("unexpected committer")
            elif field == _ENCODING_HEADER and last != _COMMITTER_HEADER:
                raise ObjectFormatException("unexpected encoding")
            last = field

def _apply_pack(self, refs):
        all_exceptions = (IOError, OSError, ChecksumMismatch, ApplyDeltaError,
                          AssertionError, socket.error, zlib.error,
                          ObjectFormatException)
        status = []
        will_send_pack = False

        for command in refs:
            if command[1] != ZERO_SHA:
                will_send_pack = True

        if will_send_pack:
            # TODO: more informative error messages than just the exception
            # string
            try:
                recv = getattr(self.proto, "recv", None)
                self.repo.object_store.add_thin_pack(self.proto.read, recv)
                status.append((b'unpack', b'ok'))
            except all_exceptions as e:
                status.append((b'unpack', str(e).replace('\n', '')))

check_identity(self._committer, "invalid committer")

        last = None
        for field, _ in _parse_message(self._chunked_text):
            if field == _TREE_HEADER and last is not None:
                raise ObjectFormatException("unexpected tree")
            elif field == _PARENT_HEADER and last not in (_PARENT_HEADER,
                                                          _TREE_HEADER):
                raise ObjectFormatException("unexpected parent")
            elif field == _AUTHOR_HEADER and last not in (_TREE_HEADER,
                                                          _PARENT_HEADER):
                raise ObjectFormatException("unexpected author")
            elif field == _COMMITTER_HEADER and last != _AUTHOR_HEADER:
                raise ObjectFormatException("unexpected committer")
            elif field == _ENCODING_HEADER and last != _COMMITTER_HEADER:
                raise ObjectFormatException("unexpected encoding")
            last = field

def check_hexsha(hex, error_msg):
    """Check if a string is a valid hex sha string.

    :param hex: Hex string to check
    :param error_msg: Error message to use in exception
    :raise ObjectFormatException: Raised when the string is not valid
    """
    if not valid_hexsha(hex):
        raise ObjectFormatException("%s %s" % (error_msg, hex))

def _parse_legacy_object(self, map):
        """Parse a legacy object, setting the raw string."""
        text = _decompress(map)
        header_end = text.find(b'\0')
        if header_end < 0:
            raise ObjectFormatException("Invalid object header, no \\0")
        self.set_raw_string(text[header_end+1:])

self._check_has_member("_object_sha", "missing object sha")
        self._check_has_member("_object_class", "missing object type")
        self._check_has_member("_name", "missing tag name")

        if not self._name:
            raise ObjectFormatException("empty tag name")

        check_hexsha(self._object_sha, "invalid object sha")

        if getattr(self, "_tagger", None):
            check_identity(self._tagger, "invalid tagger")

        last = None
        for field, _ in _parse_message(self._chunked_text):
            if field == _OBJECT_HEADER and last is not None:
                raise ObjectFormatException("unexpected object")
            elif field == _TYPE_HEADER and last != _OBJECT_HEADER:
                raise ObjectFormatException("unexpected type")
            elif field == _TAG_HEADER and last != _TYPE_HEADER:
                raise ObjectFormatException("unexpected tag name")
            elif field == _TAGGER_HEADER and last != _TAG_HEADER:
                raise ObjectFormatException("unexpected tagger")
            last = field

def check_identity(identity, error_msg):
    """Check if the specified identity is valid.

    This will raise an exception if the identity is not valid.

    Args:
      identity: Identity string
      error_msg: Error message to use in exception
    """
    email_start = identity.find(b'<')
    email_end = identity.find(b'>')
    if (email_start < 0 or email_end < 0 or email_end <= email_start
            or identity.find(b'<', email_start + 1) >= 0
            or identity.find(b'>', email_end + 1) >= 0
            or not identity.endswith(b'>')):
        raise ObjectFormatException(error_msg)

def _deserialize(self, chunks):
        """Grab the metadata attached to the tag"""
        self._tagger = None
        self._tag_time = None
        self._tag_timezone = None
        self._tag_timezone_neg_utc = False
        for field, value in _parse_message(chunks):
            if field == _OBJECT_HEADER:
                self._object_sha = value
            elif field == _TYPE_HEADER:
                obj_class = object_class(value)
                if not obj_class:
                    raise ObjectFormatException("Not a known type: %s" % value)
                self._object_class = obj_class
            elif field == _TAG_HEADER:
                self._name = value
            elif field == _TAGGER_HEADER:
                (self._tagger,
                 self._tag_time,
                 (self._tag_timezone,
                  self._tag_timezone_neg_utc)) = parse_time_entry(value)
            elif field is None:
                if value is None:
                    self._message = None
                    self._signature = None
                else:
                    try:
                        sig_idx = value.index(BEGIN_PGP_SIGNATURE)
                    except ValueError: