public override void RemovePlacement(Placement placement)
{
if (placement == FirstChild)
{
FirstChild.Parent = null;
FirstChild = null;
}
else if (placement == SecondChild)
{
SecondChild.Parent = null;
SecondChild = null;
}
else
{
FirstChild?.RemovePlacement(placement);
SecondChild?.RemovePlacement(placement);
}
}