{"ast_node_type":"other","tokens":[{"end":74,"kind":"keyword","start":0,"text":"Contravariant,"}]}
    Contravariant, // T<A> <: T<B> iff B <: A -- e.g., function param type
    Invariant,     // T<A> <: T<B> iff B == A -- e.g., type of mutable cell
    Bivariant,     // T<A> <: T<B>            -- e.g., unused type parameter