Function top_level_identifier 

pub fn top_level_identifier(
    index: &dyn CodeUnitIndex,
    target: &CodeUnit,
) -> String

The name under which target is bound in the innermost scope a file scan can reference. Only class owners are climbed: a target nested in a function is bound by its own identifier in that function’s body, never by the outer class’s or function’s name, so treating the outer name as the target’s binding attributes the outer declaration’s usages to the nested target (#3390).