Function as_general_categories 

pub fn as_general_categories<I, S>(
    categories: I,
    version: UnicodeVersion,
) -> Result<Vec<UnicodeCategory>, Error>
where
    I: IntoIterator<Item = S>,
    S: AsRef<str>,

Expand major-class designations (e.g. "N" -> Nd, Nl, No) and validate specific categories, returned in normalized_categories order.

Errors

Returns an error if an entry is neither a major class nor a known category.