From the above abi, we can see that `currency` contract accepts an action called `transfer` that accepts action with fields `from`, `to`, and `amount`.
After doing the transfer action on `currency` contract, we can verify the amount of token held by each account by looking at `currency`'s `account` table.
This table is stored on the scope of each account instead of on `currency` scope.
This table is stored on the scope of each account instead of on `currency` scope. The key of "account" is hard coded since retrieved by scope.