def addHostKey(self, hostname, key):
        """
        Add a new L{HashedEntry} to the key database.

        Note that you still need to call L{KnownHostsFile.save} if you wish
        these changes to be persisted.

        @param hostname: A hostname or IP address literal to associate with the
            new entry.
        @type hostname: L{bytes}

        @param key: The public key to associate with the new entry.
        @type key: L{Key}

        @return: The L{HashedEntry} that was added.
        @rtype: L{HashedEntry}
        """
        salt = secureRandom(20)
        keyType = key.sshType()
        entry = HashedEntry(salt, _hmacedString(salt, hostname),
                            keyType, key, None)
        self._added.append(entry)
        return entry

        Add a new L{HashedEntry} to the key database.

        Note that you still need to call L{KnownHostsFile.save} if you wish
        these changes to be persisted.

        @param hostname: A hostname or IP address literal to associate with the
            new entry.
        @type hostname: L{bytes}

        @param key: The public key to associate with the new entry.
        @type key: L{Key}

        @return: The L{HashedEntry} that was added.
        @rtype: L{HashedEntry}
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/conch/client/knownhosts.py