How to use the @loopback/repository.IsolationLevel.READ_COMMITTED function in @loopback/repository

it('should not use transaction with another repository', async () => {
          const ds2Options = Object.assign({}, dataSourceOptions);
          ds2Options.name = 'anotherDataSource';
          ds2Options.database = ds2Options.database + '_new';
          const ds2 = new juggler.DataSource(ds2Options);
          const anotherRepo = new repositoryClass(Product, ds2);
          await ds2.automigrate(Product.name);

          tx = await repo.beginTransaction(IsolationLevel.READ_COMMITTED);

          // we should reject this call with a clear error message
          // stating that transaction doesn't belong to the repository
          // and that only local transactions are supported
          // expect(
          //   await anotherRepo.create({name: 'Pencil'}, {transaction: tx}),
          // ).to.throw(/some error/);
          // see https://github.com/strongloop/loopback-next/issues/3483
          const created = await anotherRepo.create(
            {name: 'Pencil'},
            {transaction: tx},
          );
          expect(created.toObject()).to.have.properties('id', 'name');
          expect(created.id).to.be.ok();

          // for now, LB ignores the transaction so the instance

it('retrieves model instance once transaction is committed', async () => {
          tx = await repo.beginTransaction(IsolationLevel.READ_COMMITTED);
          const created = await repo.create(
            {name: 'Pencil'},
            {transaction: tx},
          );
          expect(created.toObject()).to.have.properties('id', 'name');
          expect(created.id).to.be.ok();

          await tx.commit();
          const foundOutsideTransaction = await repo.findById(created.id, {});
          expect(toJSON(created)).to.deepEqual(toJSON(foundOutsideTransaction));
        });