But, this has (or is perhaps in the process of?) gone viral and it's worth discussing.
First, the baby and Doberman are being supervised. From behind a camera, yes, but clearly this is a game they've played before, and the Doberman is a trusted family member.
Body language wise: The ears are up and forward, and Lily is doing the jump and jive playbow that I've seen Elka do so many times. She also appear to perhaps be sneaking some lick kisses in there (they're hard to catch!), and gets a good long diaper sniff when the giggling baby falls over in her hilarity. Lily is barking, frequently, but this also seems to be excited play barking. Lily also has a toy or something else she's interested in behind the little train thing by the fireplace (the sniffing, staring, and pawing are all things I recognize!), and at 2:18 or so, you can watch her go to investigate that, and very adroitly move her back end so that she neither steps on nor hip checks the baby, Addison.
I noticed the second collar right off, of course, but in the comments on the video, the owner said that it's a tone collar for training, they don't shock her. They do have an invisible fence which will shock when necessary, though, as those things do. Lily seems to check in frequently with the adults behind the camera, and I don't know if that is status quo, or if they're using the collar at the time.
And do I need to mention the baby's body language? Addison obviously adores Lily. It's both in her delighted giggles, and also at the look on her face, the clapping, the rocking on her knees. When she tips over on her back, Lily's sniffing actually seems to guide her into rolling over onto her belly. A coordinated pair!
I can see Elka playing with a baby like this, given her love of them. She's also shown herself to have fabulous self control and be much more gentle with children than she ever is with adults.