anchor.diff:      member this.UnregisterHierarchical parentIdOpt world =
           ecs.UnregisterHierarchical<'c> parentIdOpt world
   
  -    member this.Preallocate count world =
  +    member this.Expand count world =
           let mutable world = world
           for _ in 0 .. count - 1 do
               let entityId = Gen.id64
  
positive.code:     member this.System2 = system2
      member this.System3 = system3
      member this.System4 = system4
  
      member this.Contains entityId =
          cache.ContainsKey entityId
  
negative.code:     member this.Allocate comp comp2 comp3 comp4 comp5 comp6 comp7 world =
          let world =
              if unallocated.Count = 0
              then this.Expand Constants.Ecs.PreallocateAmount world
              else world
          let entityIdInv = Seq.head unallocated
          unallocated.Remove entityIdInv |> ignore
  