Function size_map 

pub fn size_map<K, V, M: Map<K, V>>(
    m: &M,
    tag: u32,
    ktag: u32,
    vtag: u32,
    stack: &mut SizeStack,
    ksize: fn(&K, u32, &mut SizeStack) -> usize,
    vsize: fn(&V, u32, &mut SizeStack) -> usize,
) -> usize