code enhancement in `sort.double_sort` (#10798)

* don't need to return list because list is mutable

* Don't need to return list as list is mutable
* use advantage of python in swapping
* filter blank inputs from input list
* minor changes

* minor mistake

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* more readable

* Update double_sort.py

* last fixes

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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* Apply suggestions from code review

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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Christian Clauss <[email protected]>