How to use the pykeepass.kdbx_parsing.common.Concatenated function in pykeepass

Struct(
        # validate payload decryption
        Checksum(
            Bytes(32),
            lambda this: this._._.header.value.dynamic_header.stream_start_bytes.data,
            this,
            # exception=CredentialsError
        ),
        "xml" / Unprotect(
            this._._.header.value.dynamic_header.protected_stream_id.data,
            this._._.header.value.dynamic_header.protected_stream_key.data,
            XML(
                IfThenElse(
                    this._._.header.value.dynamic_header.compression_flags.data.compression,
                    Decompressed(Concatenated(PayloadBlocks)),
                    Concatenated(PayloadBlocks)
                )
            )
        )
    )
)


# -------------------- Main KDBX Structure --------------------

Body = Struct(
    "transformed_key" / Computed(compute_transformed),
    "master_key" / Computed(compute_master),
    "payload" / UnpackedPayload(
        Switch(
            this._.header.value.dynamic_header.cipher_id.data,
            {'aes256': AES256Payload(GreedyBytes),

UnpackedPayload = Reparsed(
    Struct(
        # validate payload decryption
        Checksum(
            Bytes(32),
            lambda this: this._._.header.value.dynamic_header.stream_start_bytes.data,
            this,
            # exception=CredentialsError
        ),
        "xml" / Unprotect(
            this._._.header.value.dynamic_header.protected_stream_id.data,
            this._._.header.value.dynamic_header.protected_stream_key.data,
            XML(
                IfThenElse(
                    this._._.header.value.dynamic_header.compression_flags.data.compression,
                    Decompressed(Concatenated(PayloadBlocks)),
                    Concatenated(PayloadBlocks)
                )
            )
        )
    )
)


# -------------------- Main KDBX Structure --------------------

Body = Struct(
    "transformed_key" / Computed(compute_transformed),
    "master_key" / Computed(compute_master),
    "payload" / UnpackedPayload(
        Switch(
            this._.header.value.dynamic_header.cipher_id.data,

Padding(32),
    "block_data" / Prefixed(Int32ul, GreedyBytes),
    # hmac_hash has to be at the end with a pointer because it needs to
    # come after other fields
    "hmac_hash" / Pointer(
        this.hmac_hash_offset,
        Checksum(
            Bytes(32),
            compute_payload_block_hash,
            this,
            # exception=PayloadChecksumError
        )
    )
)

EncryptedPayload = Concatenated(RepeatUntil(
    lambda item, a, b: len(item.block_data) == 0,
    EncryptedPayloadBlock
))

DecryptedPayload = Switch(
    this._.header.value.dynamic_header.cipher_id.data,
    {'aes256': AES256Payload(EncryptedPayload),
     'chacha20': ChaCha20Payload(EncryptedPayload),
     'twofish': TwoFishPayload(EncryptedPayload)
     }
)


InnerHeaderItem = Struct(
    "type" / Mapping(
        Byte,