A question about etiquette on contributing to open-source projects

Hi all,

As part of my work, we use open-source rust libraries from crates.io. For one thing, we wanted extra functionality beyond what's included in a library, so we made a fork, added the functionality we wanted to see, and then submitted a PR to the repo for the library, so that it could be added to the crate if they wanted to.

This was a bit over 3 weeks ago, and our PR has had no interaction of any sort from the crate maintainers, as other, newer PRs have seen interaction (either getting merged into the same repo or seeing comments).

My question is this: what sort of reaching out to crate maintainers would be considered polite and reasonable, and what would be considered too pushy? Can I post follow-up messages on the pull request? Can I send an email to the author's email address listed in the Cargo.toml file, or to crate maintainers at their email addresses in commits (with this crate, it looks like the most active maintainers aren't the listed author)? Are there other side-channels that might be preffered?

I don't want to be pushy or overly demanding, but I'd like to know why my PR has seen no interaction even as the crate is clearly being actively maintained.