Fast subgroup check as described in issue #308

[simonmasson]

Description

closes: #XXXX

---

Before we can merge this PR, please make sure that all the following items have been
checked off. If any of the checklist items are not applicable, please leave them but
write a little note why.

• Targeted PR against correct branch (master)
• Linked to Github issue with discussion and accepted design OR have an explanation in the PR that describes this work.
• Wrote unit tests
• Updated relevant documentation in the code
• Added a relevant changelog entry to the Pending section in CHANGELOG.md
• Re-reviewed Files changed in the Github PR explorer

[weikengchen]

I found that I do not have write permission to the original branch... Can you do a cargo fmt for passing the CI's check on style?

[weikengchen]

Hi Simon, GitHub said "This branch is out-of-date with the base branch", in order to merge, you will need to update the source branch with the master branch.

Often we recommend people to submit PR from a personal account and turn on "allow maintainers to edit", so we can perform the final cleanup including fmt without interactions with the PR submitter. This can save a lot of time since we can also add necessary CHANGELOG and make the changes directly. But if the PR comes from an organization account, usually this cannot be done.

[simonmasson]

Hi. I did it in the PR #312. I close this PR