While typically the case, I can confirm there is at least one in existence. Ours was bullied by a Chihuahua when she was a young puppy, to the point where the people who got her initially had to give her up. My now wife brought her home to another doxy who was old and mostly blind, and all he did to teach her how to "dog" was dry hump her.

She's 12 now and thought being dry humped was the only way dogs played until we got a new Pomsky puppy a few weeks ago. Seeing our old doxy finally learn how to properly dog from a 12 week old puppy is amazing. But she's still a very timid and submissive little Doxy. The cat still holds a very strong hierarchy over her.

Tax: The Doxy - Pomsky duo in question - https://imgur.com/x6zfjgw.jpg