Who cleans the Personals on Aurora?

In the Robots of Dawn, Baley invites Daniel into the Personal, to which Daniel says

"It would not be appropriate for me to enter. It is not the custom for robots to enter the Personal. The interior of such a room is purely human."

For those who don't know a Personal is a Restroom or Water Closet.

Later, at the Robotics Institute, Baley requests access to a Community Personal. When they arrive the following dialogue takes place.

Giskard: "Sir, we may not enter with you."

Baley: "Yes, I am aware of that, Giskard."

Giskard: "We will not be able to guard you properly, sir."

Giskard and Daneel decide they must allow Baley enter the Personal without their protection.

When he reaches the door of the structure, Daneel wordlessly indicated the contact that would open it. Daneel did not venture to touch the contact himself. Presumable, thought Baley, to have done so without specific instructions would have indicated an intention to enter--and even the intention was not permitted.

Even with their strict instructions for the protection of Baley, they would not so much as enter the Personal (unless an immediate danger was recognized). So are there other non-humanoid robots that do the cleaning, are the Personals self cleaning, or do humans do that work?