anchor.diff:    ///  * `condition` - A delegate that specifies the filtering condition.
     [<Extension>]
     static member Where(frame:Frame<'TRowKey, 'TColumnKey>, condition:Func<_, _>) = 
  -    frame.Rows.Where(condition) |> FrameUtils.fromRows frame.IndexBuilder frame.VectorBuilder
  +    frame.Rows.Where(condition) |> FrameUtils.fromRowsAndColumnKeys frame.IndexBuilder frame.VectorBuilder frame.ColumnIndex.Keys
   
     /// Filters frame rows using the specified condtion. Returns a new data frame
     /// that contains rows for which the provided function returned false. The function
  
positive.code:   [<Extension; Obsolete("Use df.ColumnCount")>]
    static member CountColumns(frame:Frame<'R, 'C>) = frame.ColumnIndex.Mappings |> Seq.length
  
    /// Filters frame rows using the specified condtion. Returns a new data frame
    /// that contains rows for which the provided function returned false. The function
    /// is called with `KeyValuePair` containing the row key as the `Key` and `Value`
    /// gives access to the row series.
  
negative.code:   ///  * `condition` - A delegate that specifies the filtering condition.
    [<Extension>]
    static member Where(frame:Frame<'TRowKey, 'TColumnKey>, condition:Func<_, _, _>) = 
      frame.Rows.Where(condition) |> FrameUtils.fromRowsAndColumnKeys frame.IndexBuilder frame.VectorBuilder frame.ColumnIndex.Keys
  
    [<Extension>]
    static member Select(frame:Frame<'TRowKey, 'TColumnKey>, projection:Func<_, _>) = 
  