API Question Related to Cancelling Orders

Hello, i’ve been working with the Rarible API and have been able to make some good progress. However, I’d like to confirm how to cancel a transaction via the Exchange Contract. Based on the API documentation it says that there should be a method for cancel() in the exchange contract but I don’t see that in either the sourcecode or the ABI. Any help?

Regards,
Andrew

https://ropsten.etherscan.io/address/0x33Aef288C093Bf7b36fBe15c3190e616a993b0AD#code