* Support pymongo 4.x
* [pre-commit.ci] auto fixes from pre-commit.com hooks
for more information, see https://pre-commit.ci
* Fix problems detected by CI
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
* Fixing MongoDB backend to work properly with TTL
Bumping pymongo version to 3.8.0
* Updating authors
* Adding dependencies to travis config
* Fixing travis test cases
* Changing pymongo version to align with mongo result backend