How to use the co.withSharedContext function in co

* setVal(key, val) {
    return co.withSharedContext((context) => {
      context[key] = val;
    });
  }
  * getVal(key) {

* registerRollbackListenerAndThrow(listener) {
    return co.withSharedContext((context) => {
      context.currentTransaction.addRollbackListener(listener);
      throw new Error('Exception thrown');
    });
  }
}

* runMethod1InReadWrite() {
    return co.withSharedContext((context) => {
      demand(context).is.not.undefined();
      demand(context.currentTransaction).is.not.undefined();
      context.currentTransaction.isReadonly().must.be.false();
    });
  }
  * setVal(key, val) {

* runMethod1InReadonly() {
    return co.withSharedContext((context) => {
      demand(context).is.not.undefined();
      demand(context.currentTransaction).is.not.undefined();
      context.currentTransaction.isReadonly().must.be.true();
    });
  }
  * runMethod1InReadWrite() {

* getVal(key) {
    return co.withSharedContext(
      (context) =>
        context[key]
    );
  }
  * getTransaction() {

* saveTransactionAndThrow() {
    return co.withSharedContext((context) => {
      context.savedTransaction = context.currentTransaction;
      throw new Error('Exception thrown');
    });
  }
  * registerCommitListener(listener) {

* checkTransactionReused() {
    return co.withSharedContext(function* (context) {
      context.marker1 = 'the value of marker1';
      yield TransactionManager.runInTransaction(true, Util.prototype.validateMarker1, this);
    });
  }
  * delegateToReadWriteTransaction() {

* validateMarker1() {
    return co.withSharedContext((context) => {
      demand(context.marker1).be.not.undefined();
      context.marker1.must.be.equal('the value of marker1');
    });
  }
  * checkTransactionStarted() {

* mustBeInTransaction() {
    return co.withSharedContext((context) => {
      demand(context).is.not.undefined();
      demand(context.currentTransaction).is.not.undefined();
    });
  }
  * runMethod1InReadonly() {

* markTransaction() {
    return co.withSharedContext((context) => {
      context.currentTransaction.myMark = 1;
    });
  }
  * validateNoMarkInTransaction() {