This function fires an event after a token is successfully swapped
Every trade on Bancor will emit this event with information on the trade itself.
Token indexed pool,
Token indexed sourceToken,
Token indexed targetToken,
Trades on the Bancor Network are represented by a single-hop in all cases. TokensTraded event tracks the key information. The sourceAmount is provided by the trader in exchange for the targetAmount (which already has the targetTokenFee subtracted from it).
Behind the scenes, the bntAmount is the BNT volume that facilitates the trade and has the bntFee subtracted from it.