public EventMapField(EventMapConverter <TKey, TValue> converter, MapField <TKey, TValue> mapField, bool isMessageType = false)
        {
            _converter     = converter;
            _isMessageType = isMessageType;

            if (_isMessageType)
            {
                _internal = new MapField <TKey, TValue>();
                foreach (var kv in mapField)
                {
                    InternalAdd(kv.Key, kv.Value);
                }
            }
            else
            {
                _internal = mapField;
            }
        }
 public EventMapField(EventMapConverter <TKey, TValue> converter, bool isMessageType = false)
 {
     _converter     = converter;
     _internal      = new MapField <TKey, TValue>();
     _isMessageType = isMessageType;
 }