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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 create_pr_message(self, skill_git: Git, skill_repo: Repository) -> tuple: """Reads git commits from skill repo to create a list of changes as the PR content"""

        title = 'Upgrade ' + self.skill.name
        body = body_template.format(
            skill_name=self.skill.name,
            commits='\n'.join(
                ' - [{}]({})'.format(
                    skill_git.show('-s', sha, format='%s'),
                    skill_repo.get_commit(sha).html_url
                )
                for sha in skill_git.rev_list(
                    '--ancestry-path', '{}..{}'.format(self.skill.entry.sha, 'HEAD')
                ).split('\n')
            )
        )
        return title, body