def _string_to_sign(item, table_name, attribute_actions):
    # type: (dynamodb_types.ITEM, Text, AttributeActions) -> bytes
    """Generate the string to sign from an encrypted item and configuration.

    :param dict item: Encrypted DynamoDB item
    :param str table_name: Table name to use when generating the string to sign
    :param AttributeActions attribute_actions: Actions to take for item
    """
    hasher = hashes.Hash(hashes.SHA256(), backend=default_backend())
    data_to_sign = bytearray()
    data_to_sign.extend(_hash_data(hasher=hasher, data="TABLE>{}<TABLE".format(table_name).encode(TEXT_ENCODING)))
    for key in sorted(item.keys()):
        action = attribute_actions.action(key)
        if action is CryptoAction.DO_NOTHING:
            continue

        data_to_sign.extend(_hash_data(hasher=hasher, data=key.encode(TEXT_ENCODING)))

        if action is CryptoAction.SIGN_ONLY:
            data_to_sign.extend(SignatureValues.PLAINTEXT.sha256)
        else:
            data_to_sign.extend(SignatureValues.ENCRYPTED.sha256)

        data_to_sign.extend(_hash_data(hasher=hasher, data=serialize_attribute(item[key])))
    return bytes(data_to_sign)
Generate the string to sign from an encrypted item and configuration.

    :param dict item: Encrypted DynamoDB item
    :param str table_name: Table name to use when generating the string to sign
    :param AttributeActions attribute_actions: Actions to take for item