async def get_invoice(self, invoice_id, wallet: Abstract_Wallet = None):
        """
        Returns an invoice (request for outgoing payment)

        arg:str:invoice_id:The invoice ID, as seen in list_invoices
        """
        r = wallet.get_invoice(invoice_id)
        if not r:
            raise UserFacingException("Request not found")
        return wallet.export_invoice(r)

        Returns an invoice (request for outgoing payment)

        arg:str:invoice_id:The invoice ID, as seen in list_invoices
        
electrum/commands.py