anchor.diff:                      | true, x -> Some (epoch + System.TimeSpan.FromMilliseconds x)
                       | _ -> None
                   | _ -> None
  +            FlattenCollections = false
               Pack = pack
           }
   
  
positive.code:         Pack : Encoded -> Value
          EncodeDateTime : System.DateTime -> Encoded
          DecodeDateTime : Value -> option<System.DateTime>
      }
  
  type Serializer =
  
negative.code:                     | true, x -> Some x
                      | false, _ -> None
                  | _ -> None
              FlattenCollections = true
              Pack = flatten
          }
  
  