Style's font/size is set to nil by default and not override previously set style; font owns attributes are applied only when font/size is explicitly set for Style

[guzhenhuaGitHub]

I made styles like this:

let normal = Style { $0.font = UIFont.systemFont(ofSize: 8); $0.color = UIColor.black }
let red = Style { $0.color = UIColor.red }
let group = StyleGroup(base: normal, ["red": red])
"This font size is small, <red>This font size is big</red>".set(style: group) 

And the result is:

Is this a preferred effect?