Function check_mixed_case 

fn check_mixed_case(
    s: &str,
    is_fn: bool,
    allowed_patterns: &[String],
) -> Option<String>

If the string s is not mixedCase, returns a Some(String) with the suggested conversion. Otherwise, returns None.

To avoid false positives:

• lowercase strings like fn increment() or uint256 counter, are treated as mixedCase.
• test functions starting with test, invariant_ or statefulFuzz are ignored.
• user-defined patterns like ERC20 are allowed.