Certain currecny codes not implemented, e.g., SGD, CHF, AED, JPY

[shashikulk]

I am using num2words to convert amounts to words in respective currency. For example, input to my program can be 12.56 USD or 39.45 SGD, etc. I need to convert it to words in respective currency and print it on an invoice document.
But, for SGD currency, I am getting error

NotImplementedError: Currency code "SGD" not implemented for "Num2Word_EN"

I am using the below function call

num2words(Decimal(str(invoice_data['final_amount_paid'])), lang='en', to='currency', currency='SGD')

Similar error for CHF, AED and JPY currencies. I have not checked for more currencies, but at least for these 4 currencies, I am getting the above mentioned error.
For currencies like AUD, CAD, EUR, GBP, INR, USD, it is working fine.

Please help. What needs to be done to get rid of this error for these 4 currencies?