Python UT NpuMetricMonitorTest.test_npu_collector occasionally fails.

[workingloong]

The test case NpuMetricMonitorTest.test_npu_collector occasionally failed.

=================================== FAILURES ===================================
___________________ NpuMetricMonitorTest.test_npu_collector ____________________

self = <dlrover.python.tests.test_metric_monitor.NpuMetricMonitorTest testMethod=test_npu_collector>

    def test_npu_collector(self):
        with patch(
            "dlrover.python.common.metric.monitor.NpuMetricMonitor.collect_job_metrics",  # noqa
            side_effect=mock_npu_monitor_collect,
        ):
            mon = NpuMetricMonitor(
                job_name=self.job_name,
                metrics=[
                    NpuMetricEnum.NPU_UTIL,
                ],
            )
            mon.start(interval=1)
            time.sleep(2)
            mon.stop()
[2025-01-31 03:39:54,554] [INFO] [diagnosis_manager.py:220:_diagnose_metrics] Stop _metric_diagnose thread due to False
[2025-01-31 03:39:54,564] [INFO] [diagnosis_manager.py:220:_diagnose_metrics] Stop _metric_diagnose thread due to False
    
            _metric_context.log_job_metric(NpuMetricEnum.NPU_UTIL)
    
>           self.assertEqual(_metric_context.size(), 1)
E           AssertionError: 2 != 1

dlrover/python/tests/test_metric_monitor.py:1051: AssertionError
----------------------------- Captured stderr call -----------------------------