trees :: RBTreeMap :: insert_fixup_case2
it do not add black node so we do nothing else
# Case 2: parent is black
# it do not add black node so we do nothing else
private fun insert_fixup_case2(node: N) do
if node.parent.is_red then insert_fixup_case3(node)
end
lib/trees/rbtree.nit:71,2--75,4