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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 submit_completion(self, block_key, completion):
 """ Submit a completion for the service user and course. Returns a (BlockCompletion, bool) where the boolean indicates whether the given BlockCompletion was newly created. """

        return BlockCompletion.objects.submit_completion(
            user=self._user,
            course_key=self._course_key,
            block_key=block_key,
            completion=completion
        )