How to use the jrnl.util.decrypt_content function in jrnl

with open(filename, 'rb') as f:
            journal_encrypted = f.read()

        def decrypt_journal(password):
            key = make_key(password)
            try:
                plain = Fernet(key).decrypt(journal_encrypted).decode('utf-8')
                self.password = password
                return plain
            except (InvalidToken, IndexError):
                return None

        if self.password:
            return decrypt_journal(self.password)

        return util.decrypt_content(keychain=self.name, decrypt_func=decrypt_journal)

decryptor = Cipher(algorithms.AES(decryption_key), modes.CBC(iv), default_backend()).decryptor()
            try:
                plain_padded = decryptor.update(cipher) + decryptor.finalize()
                self.password = password
                if plain_padded[-1] in (" ", 32):
                    # Ancient versions of jrnl. Do not judge me.
                    return plain_padded.decode('utf-8').rstrip(" ")
                else:
                    unpadder = padding.PKCS7(algorithms.AES.block_size).unpadder()
                    plain = unpadder.update(plain_padded) + unpadder.finalize()
                    return plain.decode('utf-8')
            except ValueError:
                return None
        if self.password:
            return decrypt_journal(self.password)
        return util.decrypt_content(keychain=self.name, decrypt_func=decrypt_journal)