fix: Incorrect macro usage and redundant boolean comparison

[Anon-im]

In Rust, assert! is a macro and must be called with an exclamation mark and a condition inside the parentheses. Using assert(condition) without the exclamation mark will result in a compilation error, as assert does not exist as a function. Without fixing this, the program will not compile.

Redundant == true Check: The function valid_fn already returns a boolean value (bool). When a function already returns a boolean value (bool), an additional comparison with true or false is redundant and reduces code readability.