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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 direct_dispatch(self, arg, callback):
 """Directly dispatch a work item. This method MUST only be called from inside of another work item and will synchronously invoke the work item as if it was passed to dispatch(). Calling this method from any other thread has undefined consequences since it will be unsynchronized with respect to items dispatched from inside the background work queue itself. """


        try:
            self._current_callbacks.appendleft(callback)

            exc_info = None
            retval = None

            retval = self._routine(arg)
        except:  # pylint:disable=bare-except;We need to capture the exception and feed it back to the caller
            exc_info = sys.exc_info()
        finally:
            self._current_callbacks.popleft()

        if callback is not None and retval is not self.STILL_PENDING:
            callback(exc_info, retval)

        return retval, exc_info