anchor.diff:        sparse.GetAllIndexProperties(dict, length)
   
     ///
  -  member internal x.IsDense = 
  -    FSharp.Utils.notNull dense 
  -
  -  ///
     member internal x.HasIndex(index:uint32) = 
       if index < length then
  -      if x.IsDense then 
  +      if isDense then 
           index < uint32 dense.Length && dense.[int index].HasValue
   
         else
  
positive.code:       base.Put(string index, value)
  
      else
        if x.IsDense then
          let ii = int index
          let denseLength = uint32 dense.Length
  
  
negative.code:   member x.NewString() = x.NewString(String.Empty)
    member x.NewString(value:string) =
      let string = SO(x)
  
      // A lot faster to set the property directly instead of going through Put
      string.Properties.[0].Value.Number <- double value.Length
      string.Properties.[0].Attributes <- DescriptorAttrs.DontEnum ||| DescriptorAttrs.ReadOnly
      string.Properties.[0].HasValue <- true
  
      string.Value.Value.Clr <- value
      string.Value.Value.Tag <- TypeTags.String
      string.Value.HasValue <- true
  