Hey @Tanmaysriv, that's only a sample of using base64 encode to pass data. Do you need to pass the data as an excel file or not? if not, then you don't have to import XLSX library. You can simply follow the implementation of this base64 converter from Retool Utilities.
If you need to pass it on as an excel file, then you can follow this thread for the implementation. aturiot gave instructions on how to add the library to your app.