Read from MongoDB at sklearn (scikit-learn)

Sorry if this was asked, but I looked here and elsewhere on the internet for an answer and nothing happened.

The main use cases for sklearn are either reading from a prepared sklearn dataset into memory, or reading from a file such as .csv into memory and then processing. Can someone kindly provide an equivalent example for reading database data into sklearn for processing, preferably MongoDB, but I'll take what I can get at this point. I'm struggling a little with this now.

I can post what I have done so far, but I don't think it helps. Thanks for any help / tips / pointers.