In this PR you are trying to merge into v1 branch, is that OK? (we also have a v1.1 branch...)

@Okabe-Junya This change is actually a type of bug fix, which affects all versions. So maybe it could be merged into v0, v1 and v1.1 (but maybe it is best to leave v0? What do you think?)

Additionally, the research work for v1 and v1.1 branch has been stopped indefinitely. Is there a way to perhaps archive a branch, so that in the future we may work on it?

Semantic versioning can be very useful in solving this problem. Many OSS and software follow this rule.

Based on semantic versioning, you could do the following: archive the v1 branch, put this bugfix in v1.1 and release it (or v1.1.1??). In the future, when you add new features or bug fixes, it will be like v2 or v1.2.

The release functionality on github will be very useful to do this.