Function hash_map 

pub fn hash_map<'a, K: 'a + Hash, V: 'a + Hash, H: Hasher>(
    map: impl 'a + IntoIterator<Item = (&'a K, &'a V)>,
    hasher: &mut H,
)

Hashes a map’s entries, independently of their iteration order.

The standard library does not (yet) provide a Hash implementation for unordered map types. This can be used instead.

Note that this function is not particularly strong and does not protect against DoS attacks.