What is the syntax for Exchange Rate?

[jahagirdar]

I have a csv with the following data

...	USD	ExchangeRate
...	1200	84.01

my custom_init contains
self.header_map = {
'Date': 'date',
'Description': 'memo',
'Amount': 'amount',
'Balance': 'balance',
'Account Name':'payee',
'ExchangeRate': 'rate'

}
I assumed this will result in a {USD amount} @ {rate} entry in the output but it did not.
What do I need to do in my converter to get the desired result?