Function fold_to_map 

pub unsafe fn fold_to_map<M, K, V, K2, V2>(
    count: usize,
    keys: *mut K,
    values: *mut V,
    key_converter: impl Fn(K) -> K2,
    value_converter: impl Fn(V) -> V2,
) -> M
where
    M: FFIMapConversion<Key = K2, Value = V2>,
    K: Copy,
    V: Copy,

Safety