code: def delete_branch(self, repo, branch, prefix):
          
          # extra safeguard to make sure we are handling a bot branch here
          assert branch.startswith(prefix)
          ref = repo.get_git_ref("/".join(["heads", branch]))
          ref.delete()
docs: Deletes a branch.
          :param repo: github.Repository
          :param branch: string name of the branch to delete