How to use the scalecodec.types.U8 function in scalecodec

def ss58_decode_account_index(address, valid_address_type=42):

    account_index_bytes = ss58_decode(address, valid_address_type)

    if len(account_index_bytes) == 2:
        return U8(ScaleBytes('0x{}'.format(account_index_bytes))).decode()
    if len(account_index_bytes) == 4:
        return U16(ScaleBytes('0x{}'.format(account_index_bytes))).decode()
    if len(account_index_bytes) == 8:
        return U32(ScaleBytes('0x{}'.format(account_index_bytes))).decode()
    if len(account_index_bytes) == 16:
        return U64(ScaleBytes('0x{}'.format(account_index_bytes))).decode()
    else:
        raise ValueError("Invalid account index length")

def ss58_decode_account_index(address, valid_address_type=None):

    account_index_bytes = ss58_decode(address, valid_address_type)

    if len(account_index_bytes) == 2:
        return U8(ScaleBytes('0x{}'.format(account_index_bytes))).decode()
    if len(account_index_bytes) == 4:
        return U16(ScaleBytes('0x{}'.format(account_index_bytes))).decode()
    if len(account_index_bytes) == 8:
        return U32(ScaleBytes('0x{}'.format(account_index_bytes))).decode()
    if len(account_index_bytes) == 16:
        return U64(ScaleBytes('0x{}'.format(account_index_bytes))).decode()
    else:
        raise ValueError("Invalid account index length")

def ss58_encode_account_index(account_index, address_type=42):

    if 0 <= account_index <= 2**8 - 1:
        account_idx_encoder = U8()
    elif 2**8 <= account_index <= 2**16 - 1:
        account_idx_encoder = U16()
    elif 2**16 <= account_index <= 2**32 - 1:
        account_idx_encoder = U32()
    elif 2**32 <= account_index <= 2**64 - 1:
        account_idx_encoder = U64()
    else:
        raise ValueError("Value too large for an account index")

    return ss58_encode(account_idx_encoder.encode(account_index).data, address_type)

return self.index == 2

    def is_twox128(self):
        return self.index == 3

    def is_twox256(self):
        return self.index == 4

    def is_twox64_concat(self):
        return self.index == 5

    def is_identity(self):
        return self.index == 6


class LockPeriods(U8):
    pass


class SessionKey(H256):
    pass


class PrefabWasmModule(Struct):
    type_string = 'wasm::PrefabWasmModule'

    type_mapping = (
        ('scheduleVersion', 'Compact'),
        ('initial', 'Compact'),
        ('maximum', 'Compact'),
        ('_reserved', 'Option'),
        ('code', 'Bytes'),

def ss58_encode_account_index(account_index, address_type=42):

    if 0 <= account_index <= 2**8 - 1:
        account_idx_encoder = U8()
    elif 2**8 <= account_index <= 2**16 - 1:
        account_idx_encoder = U16()
    elif 2**16 <= account_index <= 2**32 - 1:
        account_idx_encoder = U32()
    elif 2**32 <= account_index <= 2**64 - 1:
        account_idx_encoder = U64()
    else:
        raise ValueError("Value too large for an account index")

    return ss58_encode(account_idx_encoder.encode(account_index).data, address_type)

DEFAULT_CONVICTION = 0b00000000

    value_list = ['None', 'Locked1x', 'Locked2x', 'Locked3x', 'Locked4x', 'Locked5x', 'Locked6x']


class GenericBlock(ScaleType):
    # TODO implement generic block type

    def process(self):
        raise NotImplementedError()

    def process_encode(self, value):
        raise NotImplementedError()


class GenericVote(U8):
    pass


class GenericCall(ScaleType):

    type_string = "Box"

    def __init__(self, data, **kwargs):
        self.call_index = None
        self.call_function = None
        self.call_args = []
        self.call_module = None

        super().__init__(data, **kwargs)

    def process(self):