Get a branch by using a commit #1401

The code in question is here:

repository = repo.Repo(https://....)
repo.git.checkout('dev')
specifiedCommit = repo.commit('ACommitFromMasterBranch')

Is there a way to either check whether specifiedCommit is a commit in the dev branch, or restrict somehow the commits that can be accessed to the active branch?

Currently the code above outputs the actual commit from the master branch and I couldn't find any way to access it's branch to check whether it's dev or not.