steem-python: Cancel withdrawal from vesting?

I am almost finished with a beta version of my Python GUI Wallet for STEEM. I have a couple more functions left to add, one of which is cancelling a power down. I already have the program checking if a power down is in progress or not, I just need to be able to cancel one. Is this possible in steem-python? I can't find the command for it in the documentation (steem.readthedocs.io).