Assertion: tree's leaf | /r/HasProperty | black
Facets:
Source sentences:
text: All leaves (NIL) are black.
text: Property 1 (every node is either red or black) and Property 3 (all leaves are black) always holds.
text: All paths through the deleted node will simply pass through one fewer red node, and both the deleted node's parent and child must be black, so property 3 (all leaves are black) and property 4 (