假设我有三个接口A1, B1, C1，他们都有各自的方法。
然后是三个实现类A2, B2, C2。
接下来，通过使用Mix类将三个接口包装起来。这里B2, C2接口使用了代理，而A2则通过继承获取。
问题来了，为何不能使用Mix的对象调用A1的方法？
Ugh. . .
That, m1.a(); This sentence seems not to be written in the function body, but directly under the curly braces of the class body, but it is not a statement used to declare members of the Test class.
m1.a();
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Ugh. . .
That,
m1.a();This sentence seems not to be written in the function body, but directly under the curly braces of the class body, but it is not a statement used to declare members of the Test class.