use hashmap_utils::{merge, filter_by_key, map_values, invert};
use std::collections::HashMap;

let mut map1 = HashMap::new();
map1.insert("a".to_string(), 10);
map1.insert("b".to_string(), 20);

let mut map2 = HashMap::new();
map2.insert("c".to_string(), 30);

let merged = merge(map1, map2);
let filtered = filter_by_key(merged, |k| k.starts_with("a"));
let transformed = map_values(filtered, |v| v * 2);