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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 pending_work_items(self):
        "Iterable of all pending work items."
        pending = self._conn.execute(
            "SELECT * FROM work_items WHERE job_id NOT IN (SELECT job_id FROM results)"
        )
        return (_row_to_work_item(p) for p in pending)