class Base:
    def ping(self):
        return 1


class Repo:
    def load(self, key):
        return key

    def save(self, row):
        return row


class Service(Base):
    def __init__(self, repo):
        self.repo = repo

    def run(self, key):
        row = self.repo.load(key)
        return self.repo.save(row)
