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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 handle_next_export(self):
 """ Retrieve and fully evaluate the next export task, including resolution of any sub-tasks requested by the import client such as requests for binary data, observation, etc. :return: An instance of ExportStateCache, the 'state' field contains the state of the export after running as many sub-tasks as required until completion or failure. If there were no jobs to run this returns None. :complete: A job was processed and completed. The job has been marked as complete in the database :continue: A job was processed, more information was requested and sent, but the job is still active :failed: A job was processed but an error occurred during processing :confused: A job was processed, but the importer returned a response which we couldn't recognise """

        state = None
        while True:
            state = self._handle_next_export_subtask(export_state=state)
            if state is None:
                return None
            elif state.export_task is None:
                return state