Extracting Schema Tags from a Union of Tagged Structs

const A = Schema.TaggedStruct('A', {})
const B = Schema.TaggedStruct('B', {})
const All = Schema.Union(A, B)
// Not allowed to pick from a Union
// const AllTags = Schema.pick(All, '_tag')

// this works
const AllTags = Schema.typeSchema(Schema.pluck(All, '_tag'))