key property
final
Identifies this object in a list of siblings.
SemanticsNode inherits this key, so that when the list of nodes is updated, its nodes are updated from CustomPainterSemantics with matching keys.
If this is null, the update algorithm does not guarantee which SemanticsNode will be updated using this instance.
This value is assigned to SemanticsNode.key during update.
Implementation
final Key? key;