Added Keywords to get replicasets in namespace

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<Short description of the PR>

Fixes #82

Before merge following needs to be applied:

• At least one example testcase added in testcases/
• Library Documentation regenerated according to Generate docs
• PR entry added in CHANGELOG.md in In progress section
• All new testcases tagged as prerelease along other tags to exclude it from execution until released on PyPI
• Coverage threshold increased in .coveragerc if new coverage is higher than actual, see the lint-and-coverage step in CI

fail_under = 67