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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def start_commit(self, repo_name, branch=None, parent=None, description=None):
 """ Begins the process of committing data to a Repo. Once started you can write to the Commit with PutFile and when all the data has been written you must finish the Commit with FinishCommit. NOTE, data is not persisted until FinishCommit is called. A Commit object is returned. Params: * repo_name: The name of the repo. * branch: A more convenient way to build linear chains of commits. When a commit is started with a non-empty branch the value of branch becomes an alias for the created Commit. This enables a more intuitive access pattern. When the commit is started on a branch the previous head of the branch is used as the parent of the commit. * parent: Specifies the parent Commit, upon creation the new Commit will appear identical to the parent Commit, data can safely be added to the new commit without affecting the contents of the parent Commit. You may pass "" as parentCommit in which case the new Commit will have no parent and will initially appear empty. * description: (optional) explanation of the commit for clarity. """

        req = proto.StartCommitRequest(parent=proto.Commit(repo=proto.Repo(name=repo_name), id=parent), branch=branch,
                                       description=description)
        res = self.stub.StartCommit(req, metadata=self.metadata)
        return res