Random sampling of k elements from a dask bag

It seems like there is no way, from the API, to randomly sample k elements from a dask bag.

#1332 Address a similar issue. It gives a random probability to each elements to be chosen however you are not guaranteed to have a fix number of element at the end.

Currently the way I would do it is:

import dask.bag as db
import random

data = db.from_sequence([1, 2, 3, 4, 5, 6])
random.sample(data, 3)  # [2, 4, 5]

What I think a sample method from dask.bag should do:

import dask.bag as db

data = db.from_sequence([1, 2, 3, 4, 5, 6])
data.sample(k)  # [2, 3, 6]

If this look like a desirable feature for the API I could try working on it during the next few weeks.

[eracle]

Ok, I take this issue. I am already on the way. Soon I will publish a PR and also an explanation of the proposed solution.

[jcrist]

Fixed by #6208.