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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 _get_one_pending_job(self):
 """ Retrieve a pending job. :return: A CFGJob instance or None """


        pending_job_key, pending_job = self._pending_jobs.popitem()
        pending_job_state = pending_job.state
        pending_job_call_stack = pending_job.call_stack
        pending_job_src_block_id = pending_job.src_block_id
        pending_job_src_exit_stmt_idx = pending_job.src_exit_stmt_idx

        self._deregister_analysis_job(pending_job.caller_func_addr, pending_job)

        # Let's check whether this address has been traced before.
        if pending_job_key in self._nodes:
            node = self._nodes[pending_job_key]
            if node in self.graph:
                pending_exit_addr = self._block_id_addr(pending_job_key)
                # That block has been traced before. Let's forget about it
                l.debug("Target 0x%08x has been traced before. Trying the next one...", pending_exit_addr)

                # However, we should still create the FakeRet edge
                self._graph_add_edge(pending_job_src_block_id, pending_job_key, jumpkind="Ijk_FakeRet",
                                     stmt_idx=pending_job_src_exit_stmt_idx, ins_addr=pending_job.src_exit_ins_addr)

                return None

        pending_job_state.history.jumpkind = 'Ijk_FakeRet'

        job = CFGJob(pending_job_state.addr,
                     pending_job_state,
                     self._context_sensitivity_level,
                     src_block_id=pending_job_src_block_id,
                     src_exit_stmt_idx=pending_job_src_exit_stmt_idx,
                     src_ins_addr=pending_job.src_exit_ins_addr,
                     call_stack=pending_job_call_stack,
        )
        l.debug("Tracing a missing return exit %s", self._block_id_repr(pending_job_key))

        return job