Function parse_style_class 

pub fn parse_style_class(
    name: String,
    base_attrs: &HashMap<String, String>,
    extends: Vec<String>,
    state_variants: HashMap<WidgetState, StyleProperties>,
    combined_state_variants: HashMap<StateSelector, StyleProperties>,
    layout: Option<LayoutConstraints>,
) -> Result<StyleClass, String>

Parse a style class definition