= Solution
It performs a <trial division> test for a <prime number>. An <integer> below $2$ is rejected; otherwise the function searches for a <divisor> from $2$ through $\lfloor\sqrt n\rfloor$. A <composite number> has a <prime factor> no larger than its <square root>, so finding no such <divisor> proves <primality>. For example, `mystery2(97)` returns \b[`True`], while `mystery2(91)` returns \b[`False`], since $91=7\cdot13$.
This describes the intended mathematical test. For extremely large <integers>, the floating-point computation `n**0.5` can round or overflow; an implementation intended for arbitrary-size <integers> should use an exact <integer square root>.
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