public void Add(K key, V value)
 {
     this[key] = new AssignableKeyValue <K, V>
     {
         Key   = key,
         Value = value
     };
 }
        public bool Remove(K key, V value)
        {
            var keyValue = new AssignableKeyValue <K, V>
            {
                Key   = key,
                Value = value
            };

            if (base.Contains(keyValue))
            {
                _dictionary.Remove(key);
                return(base.Remove(keyValue));
            }
            return(false);
        }