Currently

semver.parse_version_info("v0.1.0")

fails with

ValueError: v0.1.0 is not valid SemVer string

However the leading v is not included in the semver spec (https://semver.org), but the master branch of semver/semver has the following faq section - https://github.com/semver/semver/blob/master/semver.md#is-v123-a-semantic-version :

Is "v1.2.3" a semantic version?
No, "v1.2.3" is not a semantic version. However, prefixing a semantic version with a "v" is a common way (in English) to indicate it is a version number. Abbreviating "version" as "v" is often seen with version control. Example: git tag v1.2.3 -m "Release version 1.2.3", in which case "v1.2.3" is a tag name and the semantic version is "1.2.3".

The golang and go modules requires the leading v and almost every project relies with the convention (for example kubernetes/kubernetes, docker/docker and etc.).

Masterminds/semver (the golang equivalent of this project) can optionally work with a v prefix.