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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 execute(self, task):
 """ Given a task instance, this runs it. This includes handling retries & re-raising exceptions. Ex:: task = Task(async=False, retries=5) task.to_call(add, 101, 35) finished_task = gator.execute(task) :param task_id: The identifier of the task to process :type task_id: string :returns: The completed ``Task`` instance """

        try:
            return task.run()
        except Exception:
            if task.retries > 0:
                task.retries -= 1
                task.to_retrying()

                if task.async:
                    # Place it back on the queue.
                    data = task.serialize()
                    task.task_id = self.backend.push(
                        self.queue_name,
                        task.task_id,
                        data
                    )
                else:
                    return self.execute(task)
            else:
                raise