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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 _check_repos(self, repos):
 """Check if repodata urls are valid."""

        self._checking_repos = []
        self._valid_repos = []

        for repo in repos:
            worker = self.download_is_valid_url(repo)
            worker.sig_finished.connect(self._repos_checked)
            worker.repo = repo
            self._checking_repos.append(repo)