Function try_insert

pub fn try_insert<K, V>(
    map: &mut HashMap<K, V>,
    key: &K,
    value: V,
) -> Result<()>
where
    K: Eq + Hash + Clone + Debug,

Inserts a key-value pair into a HashMap if the key does not already exist.

If the key already exists, it returns an error with a message indicating the key’s existence.