Minor Description
The sampling module contains a PermutationSampler. There is scope to create a CombinationSampler too.
https://en.wikipedia.org/wiki/Permutation
https://en.wikipedia.org/wiki/Combination
If the order of the returned sample is not important then a combination can be generated faster than a permutation.
The sample can be optimised by only performing the first k or (n-k) steps from a full Fisher-Yates shuffle from the end of the domain to the start. The upper positions will then contain a random permutation sample from the domain. The lower half is then by definition also a random sample (just not in a random order). The sample is then picked using the upper or lower half depending which makes the number of steps smaller.
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