How to use the paramiko.py3compat.b function in paramiko

# indefinitely, creating a GC cycle and not letting Transport ever be
        # GC'd. it's a bug in Thread.)

        # Hold reference to 'sys' so we can test sys.modules to detect
        # interpreter shutdown.
        self.sys = sys

        # active=True occurs before the thread is launched, to avoid a race
        _active_threads.append(self)
        if self.server_mode:
            self._log(DEBUG, 'starting thread (server mode): %s' % hex(long(id(self)) & xffffffff))
        else:
            self._log(DEBUG, 'starting thread (client mode): %s' % hex(long(id(self)) & xffffffff))
        try:
            try:
                self.packetizer.write_all(b(self.local_version + '\r\n'))
                self._log(DEBUG, 'Local version/idstring: %s' % self.local_version)
                self._check_banner()
                # The above is actually very much part of the handshake, but
                # sometimes the banner can be read but the machine is not
                # responding, for example when the remote ssh daemon is loaded
                # in to memory but we can not read from the disk/spawn a new
                # shell.
                # Make sure we can specify a timeout for the initial handshake.
                # Re-use the banner timeout for now.
                self.packetizer.start_handshake(self.handshake_timeout)
                self._send_kex_init()
                self._expect_packet(MSG_KEXINIT)

                while self.active:
                    if self.packetizer.need_rekey() and not self.in_kex:
                        self._send_kex_init()

"""
        Return a "hashed" form of the hostname, as used by OpenSSH when storing
        hashed hostnames in the known_hosts file.

        :param str hostname: the hostname to hash
        :param str salt: optional salt to use when hashing (must be 20 bytes long)
        :return: the hashed hostname as a `str`
        """
        if salt is None:
            salt = os.urandom(sha1().digest_size)
        else:
            if salt.startswith('|1|'):
                salt = salt.split('|')[2]
            salt = decodebytes(b(salt))
        assert len(salt) == sha1().digest_size
        hmac = HMAC(salt, b(hostname), sha1).digest()
        hostkey = '|1|%s|%s' % (u(encodebytes(salt)), u(encodebytes(hmac)))
        return hostkey.replace('\n', '')

"""
        Return a "hashed" form of the hostname, as used by OpenSSH when storing
        hashed hostnames in the known_hosts file.

        :param str hostname: the hostname to hash
        :param str salt: optional salt to use when hashing (must be 20 bytes long)
        :return: the hashed hostname as a `str`
        """
        if salt is None:
            salt = os.urandom(sha1().digest_size)
        else:
            if salt.startswith('|1|'):
                salt = salt.split('|')[2]
            salt = decodebytes(b(salt))
        assert len(salt) == sha1().digest_size
        hmac = HMAC(salt, b(hostname), sha1).digest()
        hostkey = '|1|%s|%s' % (u(encodebytes(salt)), u(encodebytes(hmac)))
        return hostkey.replace('\n', '')

def asbytes(s):
    if not isinstance(s, bytes_types):
        if isinstance(s, string_types):
            s = b(s)
        else:
            try:
                s = s.asbytes()
            except Exception:
                raise Exception('Unknown type')
    return s

def safe_string(s):
    out = b('')
    for c in s:
        i = byte_ord(c)
        if 32 <= i <= 127:
            out += byte_chr(i)
        else:
            out += b('%%%02X' % i)
    return out

def _compute_key(self, id, nbytes):
        """id is 'A' - 'F' for the various keys used by ssh"""
        m = Message()
        m.add_mpint(self.K)
        m.add_bytes(self.H)
        m.add_byte(b(id))
        m.add_bytes(self.session_id)
        # Fallback to SHA1 for kex engines that fail to specify a hex
        # algorithm, or for e.g. transport tests that don't run kexinit.
        hash_algo = getattr(self.kex_engine, 'hash_algo', None)
        hash_select_msg = "kex engine {} specified hash_algo {!r}".format(
            self.kex_engine.__class__.__name__, hash_algo,
        )
        if hash_algo is None:
            hash_algo = sha1
            hash_select_msg += ", falling back to sha1"
        if not hasattr(self, '_logged_hash_selection'):
            self._log(DEBUG, hash_select_msg)
            setattr(self, '_logged_hash_selection', True)
        out = sofar = hash_algo(m.asbytes()).digest()
        while len(out) < nbytes:
            m = Message()

def _send_handle_response(self, request_number, handle, folder=False):
        if not issubclass(type(handle), SFTPHandle):
            # must be error code
            self._send_status(request_number, handle)
            return
        handle._set_name(b('hx%d' % self.next_handle))
        self.next_handle += 1
        if folder:
            self.folder_table[handle._get_name()] = handle
        else:
            self.file_table[handle._get_name()] = handle
        self._response(request_number, CMD_HANDLE, handle._get_name())

def safe_string(s):
    out = b('')
    for c in s:
        i = byte_ord(c)
        if 32 <= i <= 127:
            out += byte_chr(i)
        else:
            out += b('%%%02X' % i)
    return out

raise SSHException("Invalid key")

        public_keys = []
        for _ in range(num_keys):
            pubkey = Message(message.get_binary())
            if pubkey.get_text() != "ssh-ed25519":
                raise SSHException("Invalid key")
            public_keys.append(pubkey.get_binary())

        private_ciphertext = message.get_binary()
        if ciphername == "none":
            private_data = private_ciphertext
        else:
            cipher = Transport._cipher_info[ciphername]
            key = bcrypt.kdf(
                password=b(password),
                salt=bcrypt_salt,
                desired_key_bytes=cipher["key-size"] + cipher["block-size"],
                rounds=bcrypt_rounds,
                # We can't control how many rounds are on disk, so no sense
                # warning about it.
                ignore_few_rounds=True,
            )
            decryptor = Cipher(
                cipher["class"](key[: cipher["key-size"]]),
                cipher["mode"](key[cipher["key-size"] :]),
                backend=default_backend(),
            ).decryptor()
            private_data = (
                decryptor.update(private_ciphertext) + decryptor.finalize()
            )

def _read_private_key_openssh(self, lines, password):
        """
        Read the new OpenSSH SSH2 private key format available
        since OpenSSH version 6.5
        Reference:
        https://github.com/openssh/openssh-portable/blob/master/PROTOCOL.key
        """
        try:
            data = decodebytes(b("".join(lines)))
        except base64.binascii.Error as e:
            raise SSHException("base64 decoding error: {}".format(e))

        # read data struct
        auth_magic = data[:15]
        if auth_magic != OPENSSH_AUTH_MAGIC:
            raise SSHException("unexpected OpenSSH key header encountered")

        cstruct = self._uint32_cstruct_unpack(data[15:], "sssur")
        cipher, kdfname, kdf_options, num_pubkeys, remainder = cstruct
        # For now, just support 1 key.
        if num_pubkeys > 1:
            raise SSHException(
                "unsupported: private keyfile has multiple keys"
            )
        pubkey, privkey_blob = self._uint32_cstruct_unpack(remainder, "ss")