anchor.diff:  type RecordWithGenericUnion<'t> = { Id: int; GenericUnion: Maybe<'t> }
   type RecordWithDateTime = { id: int; created: DateTime }
   type RecordWithMap = { id : int; map: Map<string, string> }
  +type RecordWithArray = { id: int; arr: int[] }
  +
   let pass() = Expect.isTrue true "passed"
   let fail() = Expect.isTrue false "failed"
     
  
positive.code:       | { id = 1; age = 19 } -> pass()
        | otherwise -> fail()
  
  
      testCase "record with map" <| fun _ -> 
        let map = 
  
negative.code: 
        let record = { id = 1; map = map }
        let doc = Bson.serialize record
  
        match Bson.deserialize<RecordWithMap> doc with
        | { id = 1; map = x } -> 
          match x.["Hello"], x.["Anyone"] with 
  