This indicates that the BankAccount class is an abstract class and the withdrawal method is an abstract operation.

这表示，BankAccount类是一个抽象类，而withdrawal方法是抽象的操作。

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Conclusions Compared with traditional auscultation method, gradual withdrawal method can effectively and safely improve the rate of correct ideal anatomic placement of L-DLT.

结论 循序渐退法用于左侧双腔支气管插管，能够显著提高正确到位率。

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Conclusions Compared with traditional auscultation method, gradual withdrawal method can effectively and safely improve the rate of correct ideal anatomic placement of L-DLT.

结论 循序渐退法用于左侧双腔支气管插管，能够显著提高正确到位率。

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