Error

def generate_invoice(price_label: str, price_amount: int, currency: str, title: str,
                     description: str, payload: str, start_param: str) -> types.InputMediaInvoice:
    price = types.LabeledPrice(label=price_label, amount=price_amount)  # label - just a text, amount=10000 means 100.00
    invoice = types.Invoice(
        currency=currency,  # currency like USD
        prices=[price],  # there could be a couple of prices.
        test=True,  # if you're working with test token, else set test=False.
        name_requested=False,
        phone_requested=False,
        email_requested=False,
        shipping_address_requested=False,

        flexible=False,

        phone_to_provider=False,
        email_to_provider=False
    )
    return types.InputMediaInvoice(
        title=title,
        description=description,
        invoice=invoice,
        payload=payload.encode('UTF-8'),  # payload, which will be sent to next 2 handlers
        provider=' ',

        provider_data=types.DataJSON('{}'),

        start_param=start_param,
    )

@client.on(events.NewMessage(pattern='/pay'))
async def handler(event):
    invoice = generate_invoice(
        price_label='10 Stars',
        price_amount=500,
        currency='USD',
        title='Buy 10 Stars',
        description='Get 10 stars added to your account.',
        payload='buy_10_stars',
        start_param='pay10'
    )

    await client.send_message(
        event.chat_id,
        file=invoice,
        message='Click below to pay:',
    )