getRelations
inline fun <K : Component?, T : Component?> getRelations(): AccessorBuilder<RelationWithDataAccessor<K, T>>
Queries for a specific relation or by kind/target.
Nullability
Additional checks are done if K or T are not nullable:
K is NOT nullable => the relation must hold data.
T is NOT nullable => the relation target must also be present as a component with data on the entity.