remove method
Implementation
IHashMap<K, V> remove(K k) => new IHashMap.internal(_map.modify(k.hashCode,
(existing) => existing.filter((kv) => kv.value1 != k),
nil()));
IHashMap<K, V> remove(K k) => new IHashMap.internal(_map.modify(k.hashCode,
(existing) => existing.filter((kv) => kv.value1 != k),
nil()));