GraphQL v0.3.0 GraphQL.Lang.AST.ParallelVisitor
A ParallelVisitor runs all child visitors in parallel instead of serially like the CompositeVisitor.
In this context, ‘in parallel’ really means that for each node in the AST, each visitor will be invoked for each node in the AST, but the :break/:continue return value of enter and leave is maintained per-visitor.
This means invividual visitors can bail out of AST processing as soon as possible and not waste cycles.
This code based on the graphql-js visitInParallel function.