年龄是整数，并且必须是非负数。

Age is an integer, and must be non-negative.

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第一个基准条件用来处理非整数；第二个用来处理负整数。在小数或者负数做参数的时候，函数就会输出错误信息，返回空到调用出来表明出错了。

The first base case handles nonintegers; the second handles negative integers. In both cases, the program prints an error message and returns None to indicate that something went wrong.

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此值控制着畸变的量。负数值校正镜头圆桶状面性畸变，而整数值校正镜头针尖状点性畸变。

This value controls the amount of distortion. Negative values correct lens barrel distortion, while positive values correct lens pincushion distortion.

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