Function module_file_stem 

pub fn module_file_stem(name: &str) -> String

Return a filesystem-safe stem for the given module name.

Converts PascalCase or ALLCAPS module names to lowercase snake_case, e.g. Certificate → certificate, RFC5280 → rfc5280, AlgorithmIdentifier → algorithm_identifier.

The stem is suitable for use as a base filename with any extension.