binaryPairNodeIndex property
At one point, Talent Nodes supported the idea of "Binary Pairs": nodes that overlapped each other visually, and where activating one deactivated the other. They ended up not being used, mostly because Exclusive Sets are almost a superset of this concept, but the potential for it to be used still exists in theory. If this is ever used, this will be the index into the DestinyTalentGridDefinition.nodes property for the node that is the binary pair match to this node. Activating one deactivates the other.
Implementation
@JsonKey(name:'binaryPairNodeIndex')
int? binaryPairNodeIndex;