please help me. I have probability generating function as follows, how can get the mixture distribution of $X$ from it?

Question

$$ G_x (s)=\frac{s \cdot (1-q(1-α+α \cdot s))}{(1-q \cdot s)(1-α+α \cdot s)} $$

Or, in another way, how can I say that a random variable follows a certain distribution with a certain probability and follows another distribution with a complementary probability?

I really couldn't find what was needed and I am very grateful for the help

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