TransactionBuilder(inputs: MutableList<StateRef> = arrayListOf(), attachments: MutableList<SecureHash> = arrayListOf(), outputs: MutableList<ContractState> = arrayListOf(), commands: MutableList<Command> = arrayListOf())
A TransactionBuilder is a transaction class thats mutable (unlike the others which are all immutable). It is intended to be passed around contracts that may edit it by adding new states/commands or modifying the existing set. Then once the states and commands are right, this class can be used as a holding bucket to gather signatures from multiple parties.