public void CombineSubsets(Point point1, Point point2)
{
int index1 = BelongToSubset(point1);
int index2 = BelongToSubset(point2);
Subset sub1 = _subsets[index1];
Subset sub2 = _subsets[index2];
_subsets.RemoveAt(index2);
sub1.Combine(sub2);
}