anchor.diff:      StateBuilder : StateBuilder<'TState>
       Validators : Validator<'TCmd,'TState> list
       Handler : 'TCmd -> seq<'TEvent>
  -    Process : 'TCmd -> EventStreamProgram<CommandResult>
   }
   
   open Eventful.EventStream
  
positive.code:             new ICommandHandler<'TState,'TEvent,'TId> with 
                   member this.GetId cmd = untypedGetId sb cmd
                   member this.CmdType = typeof<'TCmd>
                   member this.Process cmd = sb.Process (cmd :?> 'TCmd)
                   member this.Handler cmd stream =
                      let unwrapper = MagicMapper.getUnwrapper<'TEvent>()
                      eventStream {
  
negative.code:             StateBuilder = stateBuilder
              Validators = List.empty
              Handler = f >> Seq.singleton
          } : CommandHandler<'TCmd, 'TState, 'TId, 'TEvent> 
  
      let toChoiceValidator cmd r =
  