Function substitute_object_escapes 

pub fn substitute_object_escapes(
    label: &str,
    ctx: &LabelSubstContext<'_>,
) -> String

Substitutes Graphviz object escapes (\N, \G, \T, \H, \E, \L) while preserving line-formatting escapes (\n, \l, \r, \\) for make_simple_label; this is strdup_and_subst_obj0(str, obj, 0) from lib/common/labels.c.