var tempDict = new Dictionary<Point, List<Point>>();
                foreach (var point1 in _filter)
                {
                    if (!tempDict.ContainsKey(point1))
                    {
                        tempDict.Add(point1, new List<Point>());
                    }

                    tempDict[point1].Add(point1);
                }

                foreach (var kvp in tempDict)
                {
                    if (kvp.Value.Count > 1)
                    {
                        foreach (var point1 in kvp.Value)
                        {
                            _filter.Remove(point1);
                        }
                    }
                }