<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def merge_user_commits(cls, commits):
 """Merge all the commits for the user. Aggregate line counts, and use the most recent commit (by date/time) as the representative commit for the user. """

        user = None
        for commit in commits:
            if not user:
                user = commit
            else:
                if commit.committer_time > user.committer_time:
                    commit.line_count += user.line_count
                    user = commit
                else:
                    user.line_count += commit.line_count
        return user