Is it possible to use Mnemonic instead of the RICs to pull data using get_timeseries?

Not directly, but you can use ```get_symbology``` to convert your code (ISIN, CUSIP, SEDOL, street ticker) into a RIC:

tr.get_symbology(['AAPL', 'IBM'], from_symbol_type='ticker', to_symbol_type='RIC')

and it will return something like this:

RIC primaryRIC

AAPL AAPL.O AAPL.O

IBM IBM IBM