Function guess_mime_type_opt 

pub fn guess_mime_type_opt<P: AsRef<Path>>(path: P) -> Option<Mime>

👎Deprecated since 2.0.0:

Use from_path(path).first() instead

Guess the MIME type of path by its extension (as defined by Path::extension()).

If path has no extension, or its extension has no known MIME type mapping, then None is returned.