pub fn document_open<'a, Pa: ParseSource<'a>, T: FromLaTeXToken<'a, Pa::Pos, Pa::Str>, Err: FnMut(String, SourceRange<Pa::Pos>, DiagnosticLevel), State: ParserState<'a, Pa, T, Err>>(
document: &mut Environment<'a, Pa::Pos, Pa::Str, T>,
p: &mut LaTeXParser<'a, Pa, T, Err, State>,
)