abstract fun generateSpend(tx: TransactionBuilder, amount: Amount<Currency>, to: CompositeKey, onlyFromParties: Set<Party>? = null): Pair<TransactionBuilder, List<CompositeKey>>
InsufficientBalanceException is thrown when a Cash Spending transaction fails because there is insufficient quantity for a given currency (and optionally set of Issuer Parties). Note: an Amount of Currency is only fungible for a given Issuer Party within a FungibleAsset