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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 _repodata_downloaded(self, worker=None, output=None, error=None):
 """Callback for _download_repodata."""

        if worker:
            self._files_downloaded.remove(worker.path)

            if worker.path in self._files_downloaded:
                self._files_downloaded.remove(worker.path)

        if len(self._files_downloaded) == 0:
            self.sig_repodata_updated.emit(list(set(self._repodata_files)))