Function zamm_yin::graph::value_wrappers::unwrap_closure

pub fn unwrap_closure<'a, 'b, 'c>(
    wrapper: &'b Option<Rc<Box<dyn KBValue + 'a>>>
) -> Option<RefMut<'b, KBClosure>>

Returns the value held by a closure StrongValue. We need a RefCell here because somehow closures are mutable when called, and the Rc that wraps a KBValue prevents mutability.