Function can_merge 

fn can_merge(class1: Option<Class>, class2: Option<Class>, text: &str) -> bool

Check if two Class can be merged together. In the following rules, “unclassified” means None basically (since it’s Option<Class>). The following rules apply:

• If two Class have the same variant, then they can be merged.
• If the other Class is unclassified and only contains white characters (backline, whitespace, etc), it can be merged.
• Class::Ident is considered the same as unclassified (because it doesn’t have an associated CSS class).