code: @Override
      public synchronized Transaction getContract() {
          checkState(multisigContract != null);
          if (stateMachine.getState() == State.PROVIDE_MULTISIG_CONTRACT_TO_SERVER) {
              stateMachine.transition(State.READY);
          }
          return multisigContract;
      }
docs: Returns the transaction that locks the money to the agreement of both parties. Do not mutate the result.
  Once this step is done, you can use {@link PaymentChannelClientState#incrementPaymentBy(Coin, KeyParameter)} to
  start paying the server.