Function parse_from_modifier_value 

fn parse_from_modifier_value<T>(
    value_span: impl FnOnce() -> Span,
    value: &str,
) -> Result<T, Error>
where
    T: FromStr,

Available on crate feature alloc and (crate features formatting or parsing) only.

Parse a modifier value using FromStr. Requires the modifier value to be valid UTF-8.